You've already gotten some good basics in this thread. When you go off-post (sorry, is that "off-base", if you're USAF) and legally retrieve your lawfully owned sidearm, you really don't have much to worry about. There's almost no such thing as a "51% bar" in Texas. Sure, there are a few in SA and other major metro areas, but unless you plan to belly up and drink hard, with nothing more than popcorn and pickled eggs for fare, chances are it's not 51%.
Sure, look for the signs, but unless the place looks, feels, and smells like a "dive", it's probably not a bar. If they have a full service food menu, it's more than likely a "restaurant", legally speaking.
Enjoy your time in Texas. Tour the historic bits of SA while you're there. Enjoy Open Carry when you return home to Nevada, and wish us well as we try to regain that basic human right here in Texas.