Im in NJ, near the Ft Dix/Maguire area. There really is no place to ride in NJ legally unless you have a plated bike. I ride in the state forests mostly and belong to a enduro club. There are plenty of hare scrambles in the area and some MX tracks if your into racing. Also plenty of enduros but you need a plated bike for them. Check out
www.ECEA.org for a list of events and local clubs. Dont rule out joining a enduro club, you dont have to race just help out with some of the clubs events, some clubs have access to private property to ride on. Check out Central Jersey Competition Riders (CJCR) or Ocean County Competition Riders (OCCR)