Steven I have only fished in Southern Utah once and I fished a creek called Mamouth Creek. It may be a little further North than you are looking for but it was a fun little creek to fish. I also fished the Fremont (sp?) River near Capitol Reef which is a little more central Utah and did very well there and had the whole river to myself.
I know there are some Utah boys on the board and am surprised they have not chimed in on this. They probably saw that you were bringing the bike and knew you would be consumed with all the awesome riding down there!
Little piece of advice for you. BRING YOUR OWN BEER!!! There beer is watery in Utah and sometimes VERY hard to find. No offense to the Utah boys on the board but you are light years away from Montana Micro brews. 😎
Joel