Flexrock 4x4 runs the event coordination between the Attica Land owner. They are still developing the means to make it a "public" park. Jeff and Mark at flex rock are also members in our club.
Our club has held some fun days and cleanup days, as other local clubs have too.
Try contacting Flexrock via their website or Facebook for information.
http://www.flexrock4x4.com/contact-us.html Stop by a Fingerlakes4x4 meeting (details posted on main page) also for more info and members benefits.
Some other "local" places to look for:
Wrangler Ave Bath NY
Back Country 4x4 play days Bath NY
Waynes world / Twisted toys Corning NY
Broome Tioga sports center Lisle, NY
Frozen Ocean Motocross Park Aurburn NY
Losts of Mud Bog events if you google NY MUDBOG EVENTS