I have taken both my dogs to dog parks many times, though the parks we go to usually don't have many dogs in them. They don't really like dog parks, because they only really want to play with each other. Where we go often though is the dog beach, where they occasionally find a great dog or dogs to join in on a game of fetch. Most often though, we play our own game of fetch and if other dogs are getting in our space we "be boring" and sit until they lose interest, then we move down the beach and resume our game of fetch.
I definitely agree that taking pit type breeds to dog parks who can get in trouble is terrible for the breed, but when you have a genuinely good dog who avoids conflict I think that going to parks can be okay. I am always watching my dogs and every other dog around my dogs, and can read body language very well. Little dogs often go after my AmStaff on walks, but generally he's safe at dog parks since those aggressive little guys are not usually there!
Little dogs are the ones I look out for with my staffy, and big dogs are the ones I have to look out for with my golden mix. He's been chased down by German Shepherds that were leashed and got away. My staffy was standing next to me and my other dog, crying, as I held the shepherds at bay and managed to pick up my golden mix (50 pounds), then the three of us went to the car which happened to be close by. I put my golden mix on the roof as the shepherds' owner caught up to grab them. My staffy was darted after once by one of the German Shepherds, but ran away just enough so that the shepherd turned back to my other dog.
My point is that no matter where you go, even if other dogs are leashed, you may not be safe. The dog parks here that I've experienced have very good reputations though and I've only seen a couple minor "fights" between dogs that were friends prior to the park. None of these were pit types, and the dogs were always fine within less than a minute after establishing their dominance. I've found that the dogs people bring to the parks I go to are not DA. I do my best to avoid conflicts with my dogs, but I also want them to enjoy life to its fullest. And the beach is their favorite place in the world!