I've written a few detailed posts about Austin over the years. I'll keep this one simple:
KAUS:
Austin Academy: Overpriced unless you just have to have a shiny new 172SP and G1000.
Streamline: Great guys...also pricy. Diamond fleet.
Compass: Very small outfit and tough to get a hold of. PM me if you want to try them. 2003 SP that rents for a bit cheaper than AAoA.
University Flying Club: Old ugly birds, but cheap and convenient. I instructed with them a lot. They'd be my recommendation, but expect to find a squawk or two or three everytime you fly.
Other Flying Clubs: Don't know anything about them, but they exist.
50R: (Lockhart)
Stenger Air: Great people. Old, but very well maintained birds. They've got a great 150, PA-28, and maybe a 172. The rates are tough to beat. From the south side of Austin, the drive is not too bad.
KHYI: (San Marcos)
I think Griffin Aviation has a 172, Arrow, and maybe something else. I've never flown with them.
KGTU: (Georgetown)
Adventure Aviation: Folded after stealing tons of money.
Pilot's Choice: I had an unpleasant time working there, but they've got a large fleet and most of the birds are pretty nice. Nothing fancy and new. Rates are pretty average, but give your instructor a tip because he's not making on the $40/hr you're paying.
There are two more schools out there that I don't know much about. Call the terminal and I'm sure they can hook you up with the info you need.