Just about every military base I have ever been to has a radio club. Check out the Ft Hood MWR website or Facebook account to see if they have a base funded repeater. 99.9% of the time, they are happy to have local residents volunteer/donate/participate at events...especially if they are held off base.
It helps to get the young, homesick soldiers/airmen/sailor/marine OUT of their dorm and out in the community. It helps morale, and probably lowers disciplinary actions too, I'd guess.
I'd be very, very surprised if it was a bunch of comm guys setting up their own repeater and locking out the community. They wouldn't be using GMRS if that was their intention