New Jack City (NJC) aka Sawtooth Canyon is a high-desert crag offering wide varieties of sport climbing routes and a few bouldering problems. Unlike most rocks in SoCal, you won't just be trying to cling to granite, here the rock is this unusal metamorphic volcanic type rock that offers a a variety of holds (edges, crimps, huecos, jugs, and underclings).
The best time to go is between October and May because, yes, it is the desert, and yes, it gets hot. The great thing about NJC is that there isn't normally much of a crowd (not nearly what you encounter at j-tree, though no trad or much bouldering here), there is free parking/camping, public restrooms nearby, and only a short approach (1-20 minutes depending on the crag). There are more than 350 sport routes, from 5.6 to 5.13.
Getting ThereDirections to NJC
From the I-15
Freeway exit Barstow Rd (HWY 247)
, go South
for about 15 miles
and turn right (West)
onto an unnamed dirt road at mile marker 63.0
Follow this road for 1 mile
and go left (South)
on the 1st road
There is no fee for camping spaces and can pretty much just pull off the road and pitch a tent. There are a few spots that have big slabs of concrete ideal for campfires. There is one public restroom building (separated 1 for male, 1 for female) that is about half a mile from most of the crags, closer to the way you come in.
Here's a great link to an 8-page pdf of a little NJC guide
also, check out the book Southern California Sport Climbing (3rd Edition) by Troy Mayr, it give beta and route descriptions of NJC and many other crags from Santa Barbara to San Diego