I've been in trout unlimited for 7 or 8 years, and fish the Guadalupe leases about once or twice a year. You don't have to access the leases, though. You can pick one of the campgrounds and presumably buy your way in. Once you're in the river, you can go anyplace you can walk to. The problem is parking.
They don't start stocking until November or so, but there are holdover fish. This year it's supposed to be tough because the water has been so low during the drought. I've heard reports of people catching fish, though.
You might consider any of the other rivers, and fish for bass instead . . . It's just a wee bit early, I think, for the Guad, but it's a great time for bass and sunfish.
Fish an olive wooly bugger with a nymph dropper and a bit of weight up the leader for either the trout or the bass.