TexasCHLforum.com

Basically it comes under two different laws, unless you have a concealed carry license from another state. Texas honors all other state licenses.

1. MPA - Motorist Protection act. Loaded inside a vehicle out of sight is legal, as long as no prohibited persons have access to it.
Without a CCL, you have to leave it in the vehicle when you are outside the vehicle.

2. Castle Doctrine - When parked for overnight the RV is considered to be the same as your house. No Prohibited Persons access still stands.

There should be some more info on http://www.handgunlaw.us/.

Have a good trip and visit.