You could try this FB page: https://www.facebook.com/groups/SAGeo/ It's the San Antonio Geocachers.There is also a CENTEX cachers Yahoo group that I've followed long before moving to the Hill Country, but it doesn't have much activity these days.
The old puzzle cache is a pretty long hike. I did it last year with RRM10 and another Kerrville cacher. We ended up with about 8.5 miles according to my GPS log but you could do it with a little less distance depending on the route you pick. Larry's earthcache, and the nearby official park cache are just a short distance from parking and the monkey rock cache mentioned earlier by TFP is a relatively short hike. If you go to the park website there's a .kml file of the park trails that you can look at in Google Earth and get a better idea of how the trails relate to the terrain and caches if you load them into GE as well.