Mapquest gives 5 returns for E85 in Austin. Not many, given the metro area includes more than a million people. I'm up on the East side of Round Rock, so the nearest one to me is actually an HEB at Parmer and I35 with the others being more Central to South Austin. :dunno: 4 of the 5 are HEB stations, so you're right that they're definitely the ones with the E85 presence here in town.
Not really sure I'd try it anyway, for the reason I posted above. Money losing deal. I don't really fret over my mileage, it's a truck, but I don't think I'd fill up with an alternative fuel knowing it was going to be more expensive to run just to have some false sense of being "green".