the Rubicon trail. You should be able to find information on line about the trail, I know there is a guy trying to organize a trip this summer on atvconnection's website. There are also outfitters around that can set you up, good luck and enjoy the ride.
What kind of rideing are you looking for? I took my family to the sand dunes in Moses Lake ,Wa. we camped right next to the lake,went boating ,road the Quads ,(jumped some dunes)went 4bying, met some good poeple, and just had a good time