Here's yet another vote for Lockhart BBQ!
Blacks for their amaaazing beef ribs, Smitty's and Kreuz for their brisket, and Chisholm Trail for their sausage.
In Austin, my lady and I enjoyed a good crawfish boil at The Boiling Pot on E 6th St. If you're not adverse to dive bars, Casino El Camino, also on E 6th St, has a great burger. And you can get your fill of authentic Tex-Mex just about anywhere.
Have a great time! If you can, let us know where you go and what you thought of it.