Polvos for Mexican food
East 6th st bars (NOT west 6th street, unless there is a good show at the Mohawk). Rainey St has beautiful bars, but on the weekend, populated with frat peeps.
Barton Springs if hot enough to swim
SOCO (South Congress) for boutiques, continental club, people watching and good coffee at Jo's
Hotel San Jose on South Congress for beer and wine cocktails in the courtyard. very nice.
Dancing/ Country/ texas swing, etc - White Horse in East Austin and The Broken Spoke in South Austin
fancy food - Backspace, East Side Showroom (!), Uchi, Uchiko, Barley Swine, Foreign and Domestic, Blue Dahlia, Wink, Boticellis
Not fancy good food - Frank, Torchys, Polvos, Bouldin Creek Cafe, Elizabeth St, Gueros, Homeslice Pizza, Shady Grove (esp after swimming), Curras, East side kings - trailer down by the east side bars.
Take a walk on Auditorium shores, or do the whole walking/ running trail starting at S. Lamar and Riverside - that will show you great views of the city and once you cross to the north side of the city, can grab coffee/ cocktail in the 2nd street or wharehouse district. btw - Frank has probably the best coffee in town even though they are a sausage joint (no, not that kind of sausage). They have a great brunch on Sundays.
If you like music stores, don't go to Waterloo - got to End of an Ear. They are across the street from Bouldin Cafe and Polvos.