Kirby is good, I don't know why so many folks are down on them. The original location is the best. They have a good tortilla soup, and their potato flautas are amazing (leftover flautas the next day are somehow even better). They also have a gluten-free menu, if you don't want to try to figure out which items do/don't have gluten in them.
Another option is any of the Alamo Drafthouse locations. Although they're not exactly a "restaurant," they do serve restaurant-quality food, and they have at least a couple of vegan-friendly dishes...plus, you get to watch a movie while you dine (and drink).