Look in the high ledges built into the wall and pick up Uzi clips and a large medi-pack. Drive up the hill and swerve to avoid the star shaped spikes. Now drive back down to the bottom of the hill and get out of the jeep. Walk up the hill and look in the overhead holes with the spikes. The hole near the top of the hill has a climbing ladder.
Jump grab to the climbing ladder, climb up to near the top and do a backwards jump.
Now get your jeep and drive up the hill. Look for climbing marks on the side of the pit. Below is a small crawlspace that you cannot climb easily into. Climb down to the crawlspace. Climb sideways next to the wall hanging on the bottom edge of the crawlspace.