Mesa Trail

I parked on Mesa Road (right near Grossmont College) down at the end of the street where you will find the main gate. The trails have clearly marked signs telling you where to go for what trail. This is useful because some of the trail heads look like small clearings off the path. Lots of hikers on these trails so bring a bell if you can. There are a decent amount of bikers here so people are very kind and let you pass.
The climb up Mesa Trail can be challenging especially on a hot summer day. There is some shady parts but it is pretty dusty the whole way up. From the top of Mesa trail you can connect up to Cowles Mountain from the Fire Road, ride a technical chunky downhill (very fun but rough) to Big Rock Park, or you can go right back down Mesa Trail to enjoy all the features you saw on the way up and thought "man if i was only going the other way".
Mesa Trail down (or mesa trail DH as its known on strava) is a flowy. more mellow version of the ride down to Big Rock Park (sorry the name of the trail escapes me). There will be people on the way down like i mentioned earlier but this track isn't particularly fast so it is easy to spot people and vice versa.
About a 20 min walk up (not ride) and about a 5 min downhill for just Mesa Trail Up and Down. Connect with Cowles Mountain for a goodwork out, you can also link up to Mission Trails.

Access Info

Mesa Road Near Grossmont College. Park near the end of the street just past the apartments.