El Alma around the Barton Springs area is one of my favorite spots, great food and amazing margs- go during happy hour for the best deals 4-7pm EVERY DAY! Best food and drink (and most interesting) in that area in my opinion.
Barley Swine would be fine solo because of the way they do seating (some bar seats, then a few long tables where they pair people up).
Thumbs up to the posts below, especially Zandunga - get a guava margarita and their guacamole! I also second Contigo - a great Austin vibe.
If you wanted to cruise Congress st for brunch I'd recommend South Congress Cafe. Could eat and drink then walk about.
Finally, this is a fun way to spend a couple hours: http://www.austineatsfoodtours.com/
Was lucky enough to be traveling to a city with a Trader Joe's and picked up some Sesame coated cashews - yum! Does anyone know if (and where) I can buy something similar in Austin? (I immediately tried Austinuts, no go)
I am also open to something similar from an online source (yup, I know how to use google, but would rather have recommendations)