Head to Morley Field in Balboa Park for college guys, contractors and business guys on their lunch break. The best times are over lunch and after office working hours for the heading home crowd. Watch the guys sitting in their cars and head back on the trails behind the bushes. Be conscious that sometimes there are lots of families there for ballgames, so head to the back trails.
Texas St. dead-ends into this part of the park, with swimming pool straight ahead. Go through the parking lot to the left and take first right around to the ball fields. Park in the spots furthest from the entrance. Guys cruising sitting there in their cars, or get out of the car and walk around in the trails west of the ball fields.