RatherBNMexico is absolutely correct. Those of us who live down in the Pine Barrens know tons of places that you can go wheeling and get her dirty, but they're kept from the public simply because of individuals who like to come tear up areas of the Pine Barrens (See the Quarter Mile) and give us a bad name. A majority of people I know (and I hope this includes you) use the land to have some fun and test the limits while getting a new muddy paint. But there are a lot of others who dump and litter, wreck ecological habitats by going off the trails, and cause a general nuisance to surround communities.
I'll give you the obvious Attison Lake and Wharton to check out. There are trail maps available at the ranger station, just stay on the trails and you'll be fine. Other then that, stay involved at places like WF or JeepForum. Get involved with the NJJA and you'll get trail rides and trail information.