If I could only have one variety for the rest of my life it would be the Italian Black.
The LSU Purple gets a lot of hate but a perfectly ripe one is crazy delicious.
In no particular order:
1. Uinta (Baba Black Lager)
2. Celis (Celis White)
3. Live Oak (Hefeweizen)
4. Saint Arnolds (Amber)
5. Normaltown Brewing (all of them)
If you are flying into Austin, I'd suggest Live Oak Brewing. It's very close to the airport if you have a few extra minutes.
Also I hope you plan on writing up a review of the places you make it to.