Mesa Trail #13 can be accessed from the main trailhead or Mesa Trail #13A. The section shown as an out-and-back is excellent when ridden downhill, but is mostly hike-a-bike if heading uphill.
The mesa loop is an intermediate cross-country trail. It is a bit faint due to low traffic, with some loose rocks and trees but the grades are fairly constant. The view from the eastern viewpoint is worth the ride, and the north section of the loop is challenging when ridden counter-clockwise as shown.
The real fun is the downhill section. It starts out smooth and flowy, then gets very steep and loose with waterbars for an additional technical challenge. Once the trail joins the arroyo, it is chunky and technical. The final section leading from the arroyo to the road is fast with tall waterbars for a little fun.