I'm not sure the real answer has been written yet. We really need to know: Where you live (at least the city especially if you live in SoCal). Do you have any watering restrictions? Do you have any shade on the lawn? Are you willing to mow 2x per week? As TW has said, if you want to kill the bermuda, wait until summer (June depending on where you live). If you want to keep the bermuda and level the lawn, also wait until June. If you want to mix bermuda with St Aug, that can be done, too. You do not have to have a monoculture. One minor problem with that is that they each thrive under different conditions. If you mow high and water once a month in the cool weather and once a week in the heat, the St Augustine will tend to overrun, but not eliminate, the bermuda. If you mow low and don't water, then the bermuda will overrun the St Augustine. If you have any shade, the bermuda will die out and St Augustine will move in.

If the surface of your yard has a good profile that drains water away from all the buildings and is pretty level (no holes), then DO NOT TILL IT. Tilling will ruin the drainage and make holes in the future as the soil settles unevenly. How far away from the beach are you? Orange county is a big place. I have seen Kentucky bluegrass growing a few miles from the beach and it looks great all winter long. KBG would suffer more the farther inland you get. If you are east of Interstate 5 down to Irvine I would not try KBG. The eastern parts of Mission Viejo would be too warm for KBG but western parts are probably fine, even though it is east of I-5. Bermuda would grow anywhere in OC as would St Augustine. You don't have to sod your entire lawn with St Augustine if you are willing to wait. If you are not willing to wait, then St Aug sod is great for an instant lawn. As Lou said above, it is a coarse bladed grass. Bermuda and KBG are fine bladed grasses. Bermuda can be much more of a pain to make really nice simply because it looks shaggy unless you mow it several times a week. It is also very invasive and tenacious. St Aug and KBG are both less invasive and much less tenacious than bermuda. And they do not need nearly as much mowing. You are asking very basic questions so I'll give you the 1-2-3 guide to growing great turf. It is really just this easy. Water deeply and infrequently. Deeply means at least an hour in every zone, all at once. Infrequently means monthly during the cool months and no more than weekly during the hottest part of summer. If your grass looks dry before the month/week is up, water longer next time. Deep watering grows deep, drought resistant roots. Infrequent watering allows the top layer of soil to dry completely which kills off many shallow rooted weeds. Mulch mow at the highest setting on your mower. Most grasses are the most dense when mowed tall. Bermuda, centipede, and bent grasses are the most dense when mowed at the lowest setting on your mower. Dense grass shades out weeds and uses less water when tall. Dense grass feeds the deep roots you're developing in 1 above. Fertilize regularly. I fertilize 4 times per year using organic fertilizer. Which fertilizer you use is much less important than numbers 1 and 2 above.

Barry I'm so glad you bumped this back up. Not sure how I missed it (repeatedly), but I disagree with much of what has been said. I don't mean to confuse you, but differing opinions usually do, so sorry in advance. St Aug should be very easy to grow in Houston. It will plow over under around and through any other grassy plants you might get including bermuda. All you have to do is mow it at the mower's highest setting every week or two. Currently it looks like you're mowing at the lowest setting. St Aug never needs to be mowed at anything lower than the highest setting. Some riding mowers will go up to 6 inches and some only go to 2-3 inches. If you're mowing at the mower's high setting now, you need a different mower. St Aug can grow up to 32 inches high and look fantastic (if you like the flowing wheat look). The taller it is the deeper the root system it gets and the (MUCH) better drought resistance you get. There is the occasional weed that will get into a thin spot, but usually you can spot spray those out with atrazine. How many thousand square feet do you have to mow? This looks below average for a new lawn, but when the lawn is so big, anything can happen. The big problem is mowing too low, but it does look like the sod went in with some bit of fungal disease. The 3rd to last picture shows some fungal lesions. I have been using ordinary corn meal to take care of fungal disease in St Aug for the past 13 years. It works for me every time. The application rate is 20 pounds per 1,000 square feet. I get it at the local feed store. It takes 3 weeks to see an improvement, but since you've already applied a chemical fungicide, corn meal won't work. Chinch bugs? You absolutely cannot see them from a photo. However, you can wipe your hand across the surface then they will flick up in the air. Put a piece of paper down and see if you can flick them up on it. There are some good YouTube videos showing how to do that. They hit the hottest part of the soil first, so that's usually next to asphalt or concrete. Then almost never begin in the middle of the yard unless you have watering issues. The first place to check would be in your last photo. And just because you might have one insect pest does not automatically make you a candidate for the full catalog of insects. And don't apply insecticide because you see bugs. Insects are not only normal, they're required for healthy soil and turf. You do have watering issues. I assume for such a large lot you have a system in the ground. It needs to be tuned up, because it is missing spots. Place some tuna or cat food cans around in the dry spots and in the green spots. Then time how long it takes to fill the cans. Some high flow systems can fill them in 20 minutes, so keep an eye on them. But some of your cans are going to be pretty dry for a long time. Eventually you want them all to fill at about the same time. Then use the time it takes to fill them as your new watering time for every zone. That's 1 inch of water. The idea is to apply a full inch all at one time. Then wait until the grass is ready for the next drink. Generally speaking when the temps are in the 90s, water once per week. With temps in the 80s water once every 2 weeks, temps in the 70s water every 3 weeks, and once a month the rest of the year. This also promotes deep roots. You don't have clay soil. You might not have perfect soil, but clay is not the issue. Usually the problem is a salt imbalance that causes soil to act like clay. Even sand can act like clay. If you really want to know all about your soil, send a sample to Logan Labs (not TAMU). For $25 they will send you a detailed report. Post that report here and morpheuspa will read it for you telling you what you need to apply, where to find it, how much, when, and how. That's another $200 value for free. Fertilize in May, late September, and again in late November. Don't try to jump the gun in the spring. If you want info on organic lawn care, let me know. I think you should, but not everyone agrees. If you go to a full chemical program, then I would suggest at least once a year to use an organic fertilizer (ordinary corn meal, again) to keep your soil biology happy. So in the long run, taking care of St Aug is easy. You water it depending on the temperature, mow at the highest setting, and fertilize 3x per year. If you do these simple things, you should never need herbicide, insecticide, or fungicide. If you see weeds in the early spring, don't use a weed-n-feed. Use a herbicide with atrazine. Read the label 2x and follow the directions carefully. Photo tip: Take garden pictures on a cloudy day to minimize contrast between bright and shadow.

Which variety for shade? Not Floratam. Or you could put in Floratam in the sunnier areas and anything else in the shady areas and let them seek their own balance with the sun and shade. Level first? Yes. If you can get it perfectly level first, you'll be happier. Kill weeds first? Yes. Spray with Round Up and start watering lightly 2x-3x daily for a week. Water just enough to keep the surface moist, NOT soggy. That will sprout lots of weed seeds. After a week spray the RU again. Then you're ready for sand/sod. Mowing high and infrequently will take out the bermuda. I would sometimes let the grass go 2-3 weeks before mowing especially in the summer heat.