This list about covers it...
https://www.movoto.com/blog/opinions...n-san-antonio/
Exploring downtown is a good start before branching out. The Alamo, Tower of the Americas, and Riverwalk (perhaps river boat tour while shopping and dining) I would make a point to see those first. After that, up to you.
And the obvious, find some great Mexican Food. I personally enjoy La Fogata and La Fonda (one on Main). Margaritas at both places are amazing.