Re: The place to go in Austin is ...
6th Street is OK, most of the fun stuff is in the warehouse district or SoCo (South Congress..)
So, if you're looking for Austin TexMex, I'd recommend Guerro's (Bill Clinton ate there, order "El Presidente" with your Hornitos Perfecta margarita!) or El Sol y La Luna, both on S. Congress. Chuy's is "the" Austin spot, but too crowded for anyone from Austin to go to often. Vivo's just east of I-35 is interesting, and has excellent cheese enchiladas. Walking around the Capital and down Congress is fun, or a walk around Lady Bird Lake is a scenic route to take. The UT campus is fun to walk around too. If you want to get out of town and see the lakes, the Oasis is a touristy spot to go, but I'd go to Iguana Grill (get the chicken flautas!).
Since you are here *this* weekend, would strongly recommend a drive out to see the bluebonnets, out 1431 is an amazing place to see them right now. East out 71 is good too. You can stay closer and see lots of wildflowers at the Lady Bird Johnson Wildflower center. Maybe get some BBQ at the Salt Lick while you're down that way. If you want bbq in town, County Line is where we take out of towners, and still one of my favorite places to go. Rudy's is all over the place and good, but I prefer Pok-E-Jo's for my close to home barbeque.
So what'dya wanna do?