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black,
As has been mentioned here previously the way to find people to ride with is to join one of the local clubs. I do not know of any clubs in NE MA but there is MVTR, Merrimack Valley Trail Riders, that meet at Freedom Cycle in Concord NH. They hold weekly rides at Hop/Ev during the summer and also put on events etc. throughout the year.
Where you are in Wilmington, MA the closest legal places to ride in MA (if dirt registered in MA) are going to be Hodges Village Dam and Franklin. Closest legal in NH (with NHOHRV tags) will be the Rockingham trail, goes from Windham to Freemont, and Hopkinton Everett Riding Area in Dunbarton.
There are numerous other areas that are not quite legal to be in that people may let you know how to get to.
As previously mentioned NEDB - New England Dirtbikes can also be a great resource for your questions.
Joel