You need to have mastered recall and distraction work with your dog before you can even THINK to begin letting him play off leash in an unfenced area. Even as well trained as my dogs are, I will not ever allow them to play and run freely off leash in an unfenced, unsecured dog park. NEVER!
You need to work first on recall. Make sure you can get your dog to come to you first time, every time, no exceptions. THEN, you need to work very hard on distraction work. Make sure without doubt that your dog will come to you no matter what he is doing; will stop on a dime when running and come when called. If your dog is not that reliable and you are not comfortable in his abilities, then you should NEVER consider taking a dog to an off leash area that is not secure.
And, this work should be done regardless of whether the area is fenced or not. You don't want to have to chase your dog if he is too far away, or if he gets into a scrape with another dog. You want your dog to respond to you when called, no matter what.
My dogs will extract themselves from a dog fight and come running to me when called. I have seen this and experienced this 3 times from my dogs (luckily we avoid most dog fights, but some do happen in parks with untrained dogs and irresponsible owners). This is how reliable you need your dog to be before exposing him to the possible risks of any dog park and gathering of a lot of dogs. It is for your dog's safety, not just because you want him to obey.
At 8 months, I truly doubt your dog is really ready for such. You'll need to work extensively at home and then take the dog to larger areas (securely fenced) and work with him on a long tether, without distractions and make sure his recall is totally reliable. THEN you need to work up from small distractions to larger ones, all with your dog under control, and work and work so that the dog understands that NO MATTER WHAT HE IS DOING, he will come to you when you call because it is going to be much better for him than whatever it is he is doing at that moment, be it playing, chasing a squirrel or fighting with another dog.
Please get a copy of "The Culture Clash" and read it before you go any further. It is a dog owner's "Bible" and should be read and understood by every boxer owner in the world, IMHO.
Good luck.