Where do you live? SoCal is not nearly specific enough. You could be in Big Bear, Newport Beach, Blythe, or somewhere else. There might be a better grass depending on your specific soil and climate.
Are you ready to mow twice a week from now on?
Are you ready to fertilize once a month?
Is your soil perfectly contoured for drainage to the sides and out to the front of your house? If not, don't do anything about that yet.

P77 is a good grass especially considering the California water situation. You might want to seed with a mixture of Yukon, Riviera, and Princess 77 at a rate of 3 pounds per 1,000 square feet.

Here are the general guidelines for bermuda as reinterpreted from The Bermuda Bible

Every month during the growing season
Fertilize with a high N fertilizer

Every week during the growing season
Water a full inch, all at one time
Mulch mow 2x at about 2 inches high

What is DG soil and what does fescue have to do with anything? Looks like you don't have a lawn at all. Is there grass there that has died? If so then we kinda need to know why it died. How often did you water it and for how long?

Please don't do any prep work on the soil until you write back with answers to the questions. Prepping for bermuda is very specific. If you start wrong you'll regret it for the next several years. If you want to do anything for your soil, then add an organic fertilizer. I like alfalfa pellets at a rate of 20 pounds per 1,000 square feet.

We live in the Inland Empire between Corona and San Bernardino where summer temps get into the high 90's-100. The house is actually my daughter's and the soil is DG (mostly decomposed granite) with a high drainage factor. All of the grassy area is flat.

There had been grass there at one time, but when they bought the house last year there was nothing as the yard had not been watered for a year or more. (Trees hadn't been watered either, but that's a whole other story.)

In the early spring last year her friend repaired the sprinkler system, tilled it, prepped it, planted fescue and watered it heavily all spring and summer. It's a fast growing water needy grass and with the conditions as they are, we'd like to help her get something with less maintenance.

We have a tifgreen hybrid Bermuda in our yard (which is predominately clay, so almost the exact opposite of her yard.) My husband and I personally like the hybrid a lot and like the fact that it goes dormant in the winter. We mow once a week in the summer and water every other morning for about 8 minutes a station I think. None of us have the time to do sod right now, so when we read that the hybrid was available in seed form, we thought that might be a good solution.

Are you afraid to say she lives in the decomposed granite foothills overlooking Riverside? Or that she lives between Chicago and Alessandro? Don't be shy. Every little bit helps. You said they rototilled. The decomposed granite in the foothills overlooking Riverside cannot be tilled. It can be jack hammered but not tilled. How deep is this soil? Can it be dug up without a jack hammer? How deep? Does high drainage factor mean that it drains fast or slow? Again, the decomposed granite I am familiar with is impervious to water. I grew up next to the orange groves (now gone) between Central and Arlington east of the 91. The foothills all around were solid decomposed granite.

Princess 77 is not Tifgreen. Calling Princess 77 a hybrid is sort of a misnomer. It is a variety of common. It is more closely related to common bermuda than to the TIF type hybrids.

Fescue is definitely not the grass to have in SoCalifornia in 2014. It needs too much water to keep it alive.

After you get the lawn changed over to something more drought friendly, you'll be changing your watering schedule to once a week during July and August. The rest of the summer it can be once every 2 weeks and monthly in the fall, winter, and spring. And yes, I realize this flies in the face of what everyone in SoCal does, but everyone in SoCal is wrong. I'm growing St Augustine in the Texas desert and have not watered my entire lawn yet this year. It's a matter of growing deep roots. That's why I need more info about her soil. If she has loose decomposed granite or soil on top of it, that's different. Need more info.