Fun sandy areas though
If you are comming from the l.a basin, take the 10 fwy, go all the way to Fontana, get off at sierra ave, turn right on sierra ave, go down and u will see TWO hills in front of you, turn right before jurupa park, and there is another hill with a WATER TANK, a big water tank above the hill, try to find your own way to the other side of it, and the starting point is at the park by a residential area.
http://www.singletracks.com/item.php?c=1&i=2149