Other than what is already mentioned, if the San Marcos outlet malls are your thing there are RV parks in Fentress Martindale and Wimberley. Gruene and New Braunfels is a short drive as well. There is Huaco Springs in NB but a bit pricy.
Within 150 miles heading south there is Potters Creek on Canyon Lake, Guadalupe PS north of SA, Huntsville SP.
Just out of that range is the KOA on Lake Livingston in Onalaska, Palmetto SP just south of Luling.
Someone mentioned Edna, we prefer Lake Texana across the street from Breckenridge but that is just our preference. Not much else out there though.
If you come to Galveston try Delanera RV park
