Utah is a great state to own an ATV. There are a number of good groups you can join if you don't have anyone to ride your ATV with or you'd like to join a larger group to find more places to ride.
One such grouping in Southern Utah is the Southeastern Utah OHV Club (SUOC). SUOC is a non-profit organization located in Castledale, Utah and this group works hard to not only to keep the land rights for ATV/OHV riders but motorcycle enthusiasts as well.
There's a lot of misinformation and a few irresponsible people have threatened to take away a lot of riding areas that responsible ATVers have enjoyed for years. SUOC works hard to maintain a good public awareness about land issues so many of the ATV trails enjoyed by off-road enthusiasts will be around for everyone who loves to ride.
SUOC is involved in trail improvements and maintenance, ATV/OHV safety and trail etiquette awareness. They also are involved in political action regarding land decisions for all recreational vehicle riders. This group did extensive work rebuilding and managing several trails in the mountains around Southern Utah to show the good that can be done when responsible groups of ATV/OHV people get together.