YEah Ok, I'm pretty sure I remember that they can't block your access to that public land. They can disallow you to park on that private road, but since that road in is the only way to access that public parcel, I seem to recall they have to allow you to pass, on foot. Similar situation I asked about in D11 and was explained how the property owners raised a big stink and got all bravo with passers by and got the green jeans called on them to give them a stearn talking to about what they can and can't do.
I'd say printout this map portion... then write onto it the phone number and name of the green jeans agent you confirmed with, and put it in plain sight on the dash or on your seat or center console. maybe even cite the CCR code number that allows your access down that road.