What type of tires do you have? There is the Cliffs Insane terrain but I wouldnt recommend going to that place with ATs in muddy conditions unless you dont mind body damage. I was out there yesterday and it was some of the best wheeling that park had in a long time because it was so dry. I was out on trail 13 and it was pretty good.
DO NOT GO TO THaT PARK BY YOURSELF!!!!! There are pits that look like a small puddle and before you know it, your front end is submerged up to the headlights and you have no way of getting out unless you have a winch.
Another place is the Badlands in Attica, IN. I will be there in Aug.