SJWMD Site: http://www.sjrwmd.com/recreationguide/palmbluff/
There are three loop trails totally 10 miles at the Palm Bluff Conservation Area, leading through sandy pineflatwoods and across a creek surrounded by cypress swamp. There is also a group camp site near the parking lot and a foul weather shelter near the creek. Great for hiking and horseback riding, but not so much for bikes due to the sand.
http://www.tripleblaze.com/trail.php?c=3&i=3072