Sunset in Fallbrook area is about 5:20 in February of 2010, so it would be full dark when the perp moves his truck from the driveway to the rear (speculative). Nor would I confine myself to the area you're describing. The area appears to be flat enough to accommodate a vehicle with or without a formal road. There is (was) a road down to the area and close to the Mcstay home from the Avocado mountain grove, and another access from an access lot off Avocado Vista. In this satellite photo, you can actually see what appear to be tire tracks in what appears to be a dirt area. The two small red dots indicate two possible access points.