If you are looking for the official rules. This time of year you're only allowed to mountain bike in WMA's on Sunday. Everyone does what they want anyway but please keep that JORBA works hard to keep access open for all of us, in addition to getting new access, but it makes it more difficult for them when mountain bikers don't follow the rules. In my opinion Allaire and the surrounding area is becoming a victim of it's own success. I partly blame Strava. Sorry but not sorry for the short rant.
Per
http://www.njfishandwildlife.com/wmaregs.htm
Mountain Biking
Mountain bicycles (non-motorized) are allowed on all roads open to motor vehicle use year-round.
Bikes are allowed on existing trails and secondary (woods) roads on Wildlife Management Areas from March 1 to April 15 and June 1 to September 15, as well as on Sundays throughout the year (see Assunpink exception in policy linked below). Use of mountain bikes is permitted year round if engaged in legal hunting and fishing activities.
Bikes are not permitted on the Highlands Trail which passes through Berkshire Valley and Wildcat Ridge WMAs. Riding over any dam, wildlife food area, cultivated fields, lawns, gardens and fire break plow-lines is prohibited. Bikers are also prohibited from establishing any new trails through the destruction of existing vegetation. For more information, see the Mountain Bike Policy linked below.
Mountain Bike Policy (pdf, 110kb)