If you do go down to 6th street take her to Pete's Piano Bar. I'm a piano player there and if you write me a note I'll get her on stage and sing her an embarrassing song or make her dance on stage or something. I'll be the piano player with the baseball hat. You could write on the note that you are from Clutchfans as we normally don't get people on stage if they don't throw some cash on the request. I agree with everyone else that the rest of 6th Street sucks.
haven't been to 6th in several months (maybe longer), but Betsy's on w. 6th and lavaca (i think) is still one of my favorite spots in austin... laid back, solid music on jukebox, small contingent of douchebags. belmont was still cool, and they serve decent food + usually have a jazz band playing inside... post grad and up corwd, nice place. union park is supposed to be pretty nice, just up 6th from belmont and betsy's. the mean-eyed cat on 5th right off mopac is one of my favorite bars in austin... completely decorated in johnny cash memorablia and art, real chill, great jukebox. agree with joejoe about 219 west... solid food, nice scene (a little trendy, but not too bad), will have live music on occassion. there's a ton more, but those are the usual spots i hit up when i'm in town. and pretty much avoid 6th street east of congress... there are some decent bars that way, but it is definitely the college crowd.
