Outdoor fresh water pool. If the sun is out and the temperature is up this is sure to be a popular spot for locals. Bring a towel to lay out and hide your food/drinks because they are "technically" not allowed. $5 to get in and head there early because the line does get long.
Great spot on UT's campus. There is a Motown exhibit going on right now.
Fun strip of ranch style houses turned bars. Popular spot for outdoor drinks during the day. Can get casual to very rowdy depending on the spot at night.
Easy half hour hike to a scenic swimming spot
There are several great outdoor breweries on East 6th st. Google austin breweries and you plan to hop around to the three mentioned above.
You can't go wrong around the city but some favorites are Verazcruz, Torchy's, Taco Joint and Texas Honey Ham.
Get out on the water. There are several rental spots. Google Congress Ave Kayaks, Rowing Dock or Austin Paddle Shack