The Blue trail is easily accessible, is great for hiking/biking, and has some great views across the lake.
Here are links to the official park site & to a trail map:
http://www.mercercountyparks.org/parks/mercer-county-park
http://www.jorba.org/sites/default/files/2010_SMART_trail_map_0.jpg
If you're going for this cache it means that either the last section of the Blue Trail is a lake, you're a completionist and have to get EVERY Blue Trail Cache, or you're lazy and drove over here to get a quick P&G. Whatever the reason, thanks for visiting! Now go get some rest. You deserve it.
ENJOY!