We live on large wooded property nearby as well. As long as our dogs stay home, they are fine. We don't take them to O'Leno at all because of the deer ticks. They have lots of warning posters about them, but people don't tend to think they are just generic warnings like any park has. In reality, its a serious problem there.
Okay, that IS creepy! I honestly don't know if there are trails. Maybe there are some weirdos around. I may have to rethink going there again.
When we were there, we had my daughters camper out on a shake-down trip close to home since she just got it. Turned out the toilet was leaking, which doesn't work for a grandma like myself. I have to pee like 4 or 5 times a night. Thankfully, we were right next to the bath house. Went in a 4:00 am one night. As I opened the door, I heard a stall door shut and lock, so I know there was another person in there too. Right as I walked in, there was a woman on the floor, in front of the sinks.
She was in in the position that Muslims pray (don't know how else to describe it) except her arms weren't outstretched. I asked her if she was okay and she said yes, she was just not feeling good. I asked her a couple more times if she needed help and she declined. I knew someone else was in a stall because I had heard it shut and lock. The first stall was empty, so I quickly used it ... couldn't hold it. No feet were showing on the floor in the back stall, so whoever it was was propped up on the toilet.
At that point, I was pretty sure it was a man in the other stall or the feet would not have been hidden. I went back out to the sinks and had to step around the floor woman's hair to wash my hands. While making a bunch of noise with water and dryer, I leaned down and whispered in her ear, asking if she needed me to call help. She still said no, she was fine.
I hightailed it back to our camper and locked the door. Pretty creepy stuff. I still don't know what was going on. Maybe there is a homeless population there? Since you saw people coming out of the woods randomly, and my late night bath house encounter, I'd guess that may be the case.
What a shame because it's a great place to kayak with the manatees.