Actually, I just did yesterday.
The road passes the ranch's gate and, if you take it straight at the creek crossing it goes to someone's property, but if you jog to the right it starts to go up the hill.
The gate at the top of the hill is a huge metal thing, I assume belonging to the Forest Service, BUT it's not locked and I opened it, drove through and closed it.
The Jeep road after that is great –lots of rocking and rolling on a sandy surface, route 1058 as mentioned.
The weird thing is, on the way back, there's a crummy old sign that says "No Trespassing" that faces AWAY from the property, so I didn't see it at all going up the hill.
I had to go back that way, legal or not, so I did. It's only a short distance between that sign and the public road in.