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
OK, maybe this isn't part of the trail, but I haven't placed a cache in a spot like this yet, so why not. Also, more caches are always better. Can be reached from the Blue Trail or driving along Conover Rd.
Bring tweezers and the writing thingy.
ENJOY!