If you seed with buffalo and don't do anything else, you will have your neighbor's bermuda for a full lawn. The buffalo will only serve to make it look weedy. However if you plug in some Tech Turf (more expensive than seeding) buffalo, you will probably have a buffalo lawn. And as TW said above, you must have full sun for buffalo and bermuda. Or in the mean time, while you're thinking about that, let's get that St Augustine going. If your temps are not in the mid 80s yet, spray with weed-b-gone (assuming you're not averse to sprays). That will take a few days to take effect but it will take out all the broad leaf weeds. Then raise your mower to the highest it will go and start mowing at that height. I know you are mowing lower than that now because you have weeds. Once you mow at the tallest height the weeds start to go away. The lawn will look straggly (not weedy) for a few weeks while all the grass grows up to the new height. But then it will look great. Then start watering but no more than once a week. You might have to water for a couple hours in each zone, but the idea is to water with enough water that the roots get water but the surface dries out completely. Weed seeds need continual moisture at the surface to germinate. If you let the soil dry out, they will not germinate. Finally FERTILIZE. NOW. If you want to use organic fertilizer, do it now and again in a month. But if you are using chemical fertilizer, then do it now before it gets hotter and then again on Labor Day. You might also get a Weed Hound tool at HD. With that tool you can remove tap rooted or bunch type weeds as fast as you can step on them. It's GREAT!

Reneenunez, you aren't allowed to "steal" a picture from someone's website....you can actually get in a fair amount of trouble for it if they decide to track you down (many images these days have tracking attached). You might be able to link the page that the image came from...most don't mind that as long as you list their site as the Name of the link.

Thanks waicklen, well since you asked...why yes, I do! This pic was taken on 6-20-10: 7-2-10, note the huge pile of crabgrass to the left...I pulled this out of the Bermuda and it's only a drop in the bucket! There was virtually no crabgrass in the Turfallo (probably because I put the cardboard and newspaper down in March - just the right time to prevent the seeds from germinating): I wasn't sure how it would respond to mowing so I had the 2nd patch (not the original test area) mowed first on 7-14-10: 7-23-10, original test patch is pretty shaggy looking at about 6-8 inches tall, 2nd patch looks good after mowing: 7-24-10 Baby's first haircut: 7-28-10, couple days after the first mowing, grass is brownish, all the green tips were cut off, I was worried... ...but it turned green again pretty quickly as you can see in the background of this pic taken on 8-12-10: I am very happy with it, it has weathered this heatwave well with very little attention, I think I watered it maybe 3 times this summer and I probably could have avoided mowing completely if I wanted to.

It very much looks like dog fennel, Eupatorium capillifolium http://www.turfgrass.ncsu.edu/Images/Plants/dogfennel/Dogfennel_field2.JPG