I would never recommend a dog park to someone who has only had the dog for a few days, especially a pit bull - that's a disaster waiting to happen.
Please understand that I am NOT anti-pit bull. In fact, I'm quite the opposite. I love them, they're wonderful dogs in the right hands. However, one cannot ignore what instincts have been bred into them since Day One.
Yes, I've seen some pit bulls do very well in dog parks, but they have always been there with their own owners - experienced owners that have put a lot of training into their dogs.