I live in New Braunfels. I've never seen an uber car pop up there on my map. I'm sure if you started in San Antonio, they would be willing to take you to NB, but they don't pick up in NB. There is a local taxi guy in NB that charges about 10 bucks a ride. I've never used him, but he's one of the first things that pops up on google.

I used uber in New Braunfels once on New Years Eve. There is one driver in the area but I think I got lucky and they were turned on for New Years.

I have also used cabs in town several times, as there are no major events going on you should be able to get one fairly easily. I usually go with New Braunfels Taxi, theu do not have meters and when you call you can ask what the fair will be from where you are to the destination.