Only one way to do it, show up or shut up!
Dave Williams, one of the "usual suspects" from Markham park MTB trails here.
It seems all parks that are volunteer maintained have the problem of many riders and few volunteers. Sorry to hear your problems with disrespectful riders and Gator Back being closed. It must be a tough trail to maintain with fall lines that erode so badly coupled with difficult access and it does have a high risk factor for injury, even by the most experienced rider.
At Markham we cut the injury rate from 4 or 5 EMS visits a week to maybe 1 or 2 a month. We did this with ability level signs and an active 30 member IMBA certified mountain bike patrol.
We have been sued a few times mostly by inexperienced riders who ignore the signs and ride onto a trail above their ability and get hurt trying to ride the trail, rather than walking it out. We defend all suits aggressively and have a good record of success based on the signs and daily patrol reports.
I am also on the mountain bike patrol at Alafia and ride there monthly. It's like a holiday away from Markham. The trails are always in amazing condition thanks to the Alafia "usual suspects". We almost always come across helmetless riders with the same comeback "we are just riding the novice trails".... then how come you are on Rock garden?? Riding without a helmet is like birth control for the shallow end of the gene pool.
The good news is that as of October 2006 mountain biking was added to the Florida Equine Law as an inherently dangerous activity. The law says "if we provide you with a piece of land to ride on and you fall down and injure yourself you cannot hold us, the landowner responsible". What it doesn't say is "unless the landowner can be proved negligent".
So, if you build a trail, maintain it as a natural area, sign it appropriately, and do not place hazards on the trail it will be difficult to prove negligence and the Equine Law will (hopefully) prevail.
We share similar problems and it's good to share solutions to protect the trails for future generations of MTN bike riders.
Ride on. Dave
turnerburner@bellsouth.net