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
There certainly are a lot of trees down in these here woods. Certainly wood be a good place to hide something. Hmmmm..
This is the biggest cache of the bunch, but you still need a pen.
ENJOY!