USGS interactive map shows them within about 30 mi - San Gabrielhttps://nas.er.usgs.gov/viewer/omap.aspx?SpeciesID=443
the biggest I've ever seen wild are on the lower Frio south of the town of Sabinal, but the upper Sabinal R. has some beauties (below, really close to Utopia, and sight-fishing).
Big enough to eat a size 8 cats whisker, and measures out 11"
Sabinal is also one of the best bass rivers in Texas.
Cibolo Creek around Herff Springs and the Boerne Nature Center has some big ones.
Shonto Ranch, a private game ranch with pay fishing, on Turtle Creek just west of Kerrville, has Rio Grande cichlids over 3 lbs - pellet fed, but they also eat what the creek provides.