It's definitely nice to have a car to check out downtown SA (riverwalk, alamo, USO) and the surrounding attractions on the weekend as well as the occasional drive to the commissary since it's a bit of a walk. That being said, don't go out of your way to drive from significant distances because we often pooled our money for taxis, rode buses or bummed rides from those with cars anyway. There's also an Enterprise at Ft Sam so you can rent for a weekend and share the costs with friends. It all depends on how much you're planning on using it, how far you're driving from, and whether you're planning on drinking when you go out as well, in which case, you're going to want a taxi anyway.