Here's a link
to a list of free trout fishing spots along the lower Guadalupe. Rio Raft is free for the 1st 10 people per day. I have not fished it yet, but it is in the trophy trout zone, so may be worth it if you want to catch a big one.
“No man ever steps in the same river twice, for it's not the same river and he's not the same man.” -Heraclitus