El Prieto Trail
Moderate. (temperature effects the difficulty of the hike greatly as more than half of it has NO shade cover)
Spring, Summer, Fall, Winter.
From the 210FWY exit N. Windsor Ave and drive north. Just before the street hits a 90º right turn there will be a parking lot on the left. Park here. No permits required. I have never had issues finding parking though the lot can get full. This is considered "Oak Grove Park."
The treck begins at the parking lot. As you head North there is a road that goes down to the JPL overflow parking lot, a path up to a park typically occupied by vagrants and then the fire road which is where you should head.
None of the trails seem to be well documented even though they are certainly well traveled. This loop is often occupied by hiker, bikers and horses. Most bikes will head West up the fire road and either come back down the same way as an out and back, or loop the entire El Prieto fire road cutting back through neighborhoods. More experienced riders may opt for the reverse route of my hike which has more obstacles and switch backs on the way down.