We recently bought a Roadtrek van conversion RV to see more of the States and Texas in particular. We often spend weekends in the Texas state parks and it has been my experience that there are between 3-7 caches in these parks. Bastrop, Misson Tejas, Brazos Bend all have caches to name a few.
I do most of my prep at home. I use a Garmin 60cs, GSAK and Mapsource in various combinations to preload the caches around the park we're visiting. I have the auto navigation kit for 60cs as well and use it for driving too. Once at the park, my wife and I typically hike from the campground to the caches. we're also planning to add a bike rack to allow us to bring our bikes along.
Hope this helps.
Barry