About 40 minutes. Park at the Courthouse Loop South Trailhead, and start hiking east on the golfcart-wide trail. Follow the signs for Big Park Loop (right, left, then 0.4 miles then right again). Continue heading east PAST the tower till you can see a ledge ramp system with trees from the right that heads up to the base. Leave the trail just before it turns right into the wash, and follow up the gully briefly before turning left onto that tree ramp, and follow that tree ramp to the end. It cliffs out right at the start of the climb!
Thanks to Jason Nelson's comment for the original approach beta!