Visited there several times, but long before I began my coin collecting. Sorry I can't offer any help with coin shops. But in general the Riverwalk was nice (bent too many elbows at the "Howl At The Moon Saloon"!). As a kid growing up with Fess Parker and Buddy Ebsen the Alamo was such a treat to see for real! Took my wife on the Spanish Missions route. Visited every one. And back then the Lone Star Brewery was still active. Great tour of their museum.
I you find a good one let me know. I am about the same distance from Houston as SA. Haven't found any good ones in Houston.