Hey #82,
Moab is a great place for the trials bike! You can ride the slickrock trail with motorcycles. Contrary to what most mountain bikers think, the trail was actually laid out by motorcyclists, for motorcycles in 1969. You'll get a few dirty looks, but most bikers are pretty cool and very interested in our bikes. I think they are a bit jealous watching how easy the hills are when you have an engine
There is a pretty cool OHV area designated for use by 4x4's and other motorized vehicles called Area BFE. I think the local club has put on some events there in the past.
Check out the website http://areabfe.com/
A lot of the jeep trails are pretty good rides, too. We try to pick out the more difficult rated trails. Gas can sometimes be an issue with the trials bikes, so we always carry some extra fuel and try to ride the shorter trails. Some favorites are Seven Mile Rim, Moab Rim, Poison Spider Mesa, and the many near Gold Bar Rim area.
http://www.4x4now.com/mu4wd.htm
See ya,
Dana