There is some gorgeous water upstream of Kerrville on both forks of the Guadalupe. Get yourself a copy of Kevin Hutchison's book Fly Fishing the Texas Hill Country. Though slightly dated, it still has the latest and most thorough set of descriptions of all the Hill Country rivers, including mile by mile access points, etc. Be aware that Kendall County has a law that prohibits accessing the river at bridges and river crossings (to cut down on tubers, mostly). That includes the area near Sisterdale.
Fish Friendly -- Life's too short to do it any other way