About 10 miles of mostly beginner and some intermediate scenic trail. Completely flat. Beginners will be right at home on these trails. Intermediates will find trails to be easy, fun to ride in large groups, and good for introducing beginners. Experts: You're going to the beach anyway so you might as well get a short ride in! Not challenging at all.
From the South: Take I-95 North and exit East on SR 207. About 7 miles later you'll need to head north on US 1 and then north on SR A1A. From the North: Take I-10 to I-95 South. From I-95 South, exit on SR 202 and head South on A1A from Ponte Vedra. There are several signs for Guana River State Park, but you want the main entrance (not the beach area). Pay the entrance fee and park on the west side of dam. No, there's no shade.
http://www.singletracks.com/item.php?c=1&i=2761