"What's going on at the oil derricks in El Burro Heights? Why are there so many private security guards patrolling it around the clock? Whatever it is, they're not about to let anybody just walk in there and find out. Be prepared for multiple ambushes that escalate in severity with each wave of attack."
One of the easiest ways to survive this Survival is to camp in the shed on the west of the area, it provides cover from the Buzzards when they come, and has many places you can go behind to provide cover from enemy fire.
Another way is to hide in one of the empty waste boxes in the south of the area, although this provides good cover from all angles, the Buzzards can get to you, so be careful in Buzzard-spawning rounds.