I don't know of any Confederate Cemeteries in San Antonio or Galveston, but there very well may be some. However, the Texas State Cemetery at Austin has a Confederate section. I learned about this when I was researching my gg-grandfather, who is buried there. They have a well organized website and you shouldn't have any trouble locating it in a simple search. Also, The Handbook of Texas Online can answer almost any question you can ask regarding Texas. Good luck.