I took my son and grand daughter over the Otay Mountain truck trail here is San Diego. Otay Mountain is located on the border of Mexico and Otay Mesa here in southern San Diego. We accessed the trail from Alta Road which is off the 905 highway that runs along the border.
The west access we took was recently oiled to keep the dust down. My jeep is now well lubed (only 146 miles on it). This isn't technically challenging other than you need to stay on the trail as the drop off is a thousand feet or better in some spots. The trail is over 12 miles in length and will take a couple of hours.
The east side is less well kept and the trail is quite narrow. There is an offset, or mid trail that can take you just east of the Upper Otay Lake, however, that run is usually really washed out, so be warned.
This trail has our Border Patrol/Homeland Security folks actively working the area. They are good folks and will let you know if and when the trail is closed.
Here are some pictures of the trip: