To get to the climbing areas, park at the Paso Picacho Campground ($6.00/day parking fee) and ascend the trail to Stonewall Peak. Just before you get to the rails at the top you can scramble west to approach the Upper Tier, or continue up and over the rails to the south and down and thru blocks to reach the lower tier. The approach for the lower tiers is not for the faint of heart so be prepared for some moderately difficult bushwacking, scrambling and routefinding.
I've added this section to make anyone considering a trip to the area aware of some very good climbing opportunities. I won't go into specifics about the routes (see "Rock Climbers Guide to San Diego County" - Dave Kennedy and Chris Hubbard) but will mention a few that I've done in an effort to make more people aware of this fine area. The book lists many routes, or you can do like me and blow off the guide and go for whatever looks like a fun line.
Upper Tier: there are a few routes available here, 2 of which were established during the Sierra Club RCS era. Directly below the summit guardrails are a 5.9 (leftmost line that splits at the top) and a 5.6 just to the right of the 5.9. Both can be protected w/ traditional gear and natural anchors. Be aware that the 5.9 is kinda old-school so be ready for a tricky move past the 2nd placement. 2 finishes: left (5.8-ish) or right on the seam (5-hard.) I believe there is also a 5.7 further to the right but have not verified this.
Lower Tier: quite a few climbs can be found here, many of which were FA'ed by Werner Landry and still sport the same coffin-nails he and others originally installed. In short, the area doesn't get a lot of traffic so beware of loose flakes and shaky bolts. Have your belayer don a brain bucket 'cuz they are going to get pelted by small rockfall. If you're looking to rack up karma points, bring your bolt kit along and replace some of the old 1/4" stuff (but please respect the FA and don't put in new placements or anchors without permission.)
Down on the lowest portion of the lower tier is a route called Frito Bandito - highly recommended. This is a 1-pitch 5.8 adventure climb w/ great trad placements and the full spectrum of 5.8 ground - friction, finger crack, lieback flakes, routefinding, etc. 2 bolts are to be found on the blank slab just below the topout, otherwise this is a wandering fun route w/ some challenging moves for the grade. Bring lots of slings and extend everything. Walk off the back.
Trad rack, a few quickdraws. You'll need a 60m shot for Frito Bandito. Bring a ropebag and a helmet too. Mostly traditional pro, small and up to 4".