I'm not sure why you'd be concerned about the popular areas of RVing in south Texas. Have you heard of a lot of crime caused by the border crossers? I haven't. It's not their intent to hang around once crossing and in the majority of cases they can't hang around. They are processed by the Border Patrol and sent elsewhere. There is more crime in any city in the U.S.
We love the Hill Country and Rockport areas but it can get cool/cold at times. The McAllen area is a LOT warmer.