RB is Rancho Bernardo. 4 corners is the parking lot/gathering spot for coral canyon OHV. It's out by Alpine, in the Cleveland National Forest. Take 8 East and get off on Buckman Springs Road. Pass the high school (it's on your left), keep your eyes peeled for the sign to Coral Canyon OHV (it will be on your right). Follow that road for a few miles and you will end up at four corners. That road is not pleasant to drive on...too bumpy for me, so I air down and disconnect as soon as I make the turn. Smooths everything out! LOL!
If it makes you more comfortable, we can meet somewhere locally and head out there together.