The daily use fee has increased to $6/person, as of '08. Seniors and youth discounts still apply - $4/person use fee.
Also, evidently a mountain lion has taken the canyons and gullies surrounding The Castle to residence. Solo hikers/climbers should be aware.
Note updates (Oct 2013) to seasons of operation (1 Oct = winter) and fees ($9/adult/day), plus website info: