In my area, most dog parks don't allow dogs that aren't fixed.
There are exceptions to every rule but I would say an unaltered male pitbull is a no-no.
I say that as the owner of a fixed male pit, that gets bullied by my shi tzu...
Almost every male pit I have ever seen, that isn't fixed, had problems at dog parks.
Not being fixed for any adult male dog adds a whole other level of seriousness to most dog play.
Pits being a fighting breed, that initial posturing thing that dogs do to signal play, pits usually take that very very seriously and have the tendency to want to fight instead of play.
The hormones and dominance that unaltered male dogs display, tends to change the vibe in a group of dogs.
If you have a male dog, especially a male pit, you must know the signs that a fight is about to start and control it before it happens.
You can usually stop a male pit if you catch him when he first starts posturing...
A female pit, when she is in fight mode, is usually ready to kill, no posturing, no pretending they go right in for the kill.
Most unaltered male dogs will try to hump the shit out of every female in the park.
When I had a female dog, it used to annoy the shit out of me. most owners don't say anything or stop the behavior