Does anyone know what mexican restaurant in San Antonio, TX serves agua de horchata?

Blanco Cafe sells it. Also, some Walgreens stores and supermarkets sell it in a bottle. You can also find a recipe at this site (if nothing else, you could give it a try making it yourself):

http://www.dallasnews.com/sharedcontent/dws/fea/ta...

There used to be one in Houston that served it, but that was 15 years ago. All I remember was that it was beside an HEB Pantry store. I haven't ever been able to find horchata since then. It's so good! Maybe there's a recipe for it. Good luck!

La Palatera on Blanco Rd.

http://www.findmexicanrestaurants.com/ has a list of mexican restaurants around the U.S. I'm sure you'll find at least 30 of them in San Antonio

Taco Haven in Southtown

Unquestionably the Mexican Market on Commerce will have the best restaurants in town that are authentically Mexican with the old fashioned atmosphere of the flaminco dancing on weekends and then on to the restaurants with mariachis and what restaurant doesn't have their special blend of margaritas. If you head north on Broadway there is the Tomatillos, but you may or may not have a Mariachi Band. At Mi Tierra with all the lights and busy busy traffic, you will be guaranteed a good time. It is open 24 hours a day. I have been there all hours and have always had a good meal and there has always been mariachis. On Weekends there is always something special going down at the El Mercado (Mexican Market).

Pretty much any of the ones along Pinn Road have it. Molino's on Potranco has it.

Many of the jalisco restaurants do

if your talking about that drink they serve it at jaliscos and thay have several of them around SA