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
It's so cool how there are all these little side pathes which I didn't know about before placing all these caches. I had originally wanted to place this one under the bridge just down the way from this site, but it was too close to someone else's cache. Well, I just found myself a backdoor into this area of the park. NICE!
Hope you brought a pen.
ENJOY!