All of the trail is double-track gravel and flat. There are a few slightly rougher spots with larger pieces of rocks but most of it is pretty well ridden and smooth. Keep you eyes peeled for alligators, they are numerous and may be on the trail. Wide open so be prepared because you don't want to walk back from five or ten miles out.
Start either at the parking lot at Atlantic or behind Markham Park.
http://www.singletracks.com/item.php?c=1&i=9864