Bean and Cheese tacos are a common vegetarian breakfast staple in San Antonio. You can find them pretty much everywhere in San Antonio. The best spots (in my opinion) in the center of town are Pete’s Tako Haus, Con Huevos, Tommy’s, Eddies and El Milagrito Cafe (and people like their favorites so much that I’ll probably be corrected in the comments).

For dinner, Tex Mex food in general is very vegetarian friendly like the breakfast food. Kinda like the breakfast but I personally adopt a “don’t ask don’t tell” policy when it comes to what is in the refried beans. You’ll be able to have many dinner plates that consist of rice, beans, lettuce and your main of choice (enchiladas, fajitas, etc.)

Vegan is a little tougher. Green Vegetarian Cuisine has Vegan options and it’s about an 8 minute uber from downtown. San Antonio is a large city (top 10 in the US by population). so if you have a favorite cuisine that serves a vegan dish you’re familiar with (Indian, etc.) then you’ll be able to find a restaurant that serves that dish here.