On Post road about one mile south of I-240. You can't exit onto Post road from 240. Instead, exit at Douglas Blvd, turn north for a very short distance, and then turn East on 74th. Take it one mile to Post road and turn south.
Parking lot is about one mile on the left.
I particularly like the yellow trail myself. The green trail has some sand and is less challenging than the yellow trail. However, on the green trail, there is the Gravity Playground. It is several huge drop offs into a large creek. The drops are probably about 25 to 30 feet and you can get hurt if you're not careful.