You could go to 42nd st, take the NJ Transit #166 and get off at Broad Avenue & Van Nostrand, walk up the hill on Van Nostrand. Or if you closer to upper Manhattan, from GWB terminal at 178th st, take any NJ Transit 171, 175, 178, or even the Jitney "Paterson " vans. Stop at Route 4 and Jones Road(closest), or Route 4 and Broad. Walk on either roadway to Van Nostrand and go up the hill into Flat Rock Brook.
Take the M20 bus in NYC to the 166 bus and walk about 16 min. That was the easiest route I found.
bus terminal at George Washington bridge bus# 178, get off at Jones road in the middle of route 4 walk up the road and turn right at the corner walk to the stop sign and make a right walk up the hill and your there
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