Main Divide:
http://blog.nextstepdesigns.com/?cat=18 (scroll through till you see it), which is accessible by heading back into Silverado canyon (not far from Lake Irvine). Also there is the Irvine Lake Off Road Park, but that is not really for normal vehicles, it's more for tricked out pre-runers or extreme rock crawlers.
Azusa Canyon is not too far, but small.
http://blog.nextstepdesigns.com/?cat=13 There is a long trail up and over the ridge there called RinCon that is really really easy, but still kinda interesting. It's free, but you have to get the gate code from teh ranger station at Azusa.
Gorman/Hungry Valley area has tons of trails, including the challeging Miller Jeep Trail, but I think that area is on fire right now...
Another FUN trail besides Cleghorn (
http://blog.nextstepdesigns.com/?cat=14) is Area 51/Rowher Flats, off the 14 freeway near Santa Clarita.
Are you a member of
www.sclr.org? That's teh best way to get clued in to the local Land Rover scene.
Regards,
NW