Big Bend (both the National and State) Parks are NOT to be missed. But both require plenty of preparatory work, as in maps and GPS's, before attempting to do on one's own. Chuck Cypert, DORBA member, wrote a book on "Mountain Biking Texas & Oklahoma" first (1995) & second (2002) additions although a little dated now have many good comments about negotiating trails in the National Park. As Chuck has said, "Survival in the Big Bend is not by chance!" Also consider getting in touch with Mike Long, trail guide from Desert Sports in Lajitus, TX for the low down.
Rowlett Creek Preserve