With Dutch, we frequented a couple of dog parks when he was much younger, but there were never any dogs there, and that is why we went. At that time all we wanted was just a space for him to stretch his legs and run....because of his age, if another dog we didn't know showed up, we usually left. Dutch got lots of socialization with people and other dogs, but I just did it in a more controlled environment with dogs that I knew.
When he was about 6 months old I started trying him out at our local dog park which is frequented by lots of dogs, at first it was great, Dutch had so much fun, and I loved how exhausted he was when we got him home. But, I started to notice "bad habits" forming very quickly...like the barking in others faces, and also there was a couple of other dogs there that started to get a real hate on for Dutch and would "pin" him constantly. I actually posted a thread asking for advice on the subject, and based on my feelings, and the advice and support from fellow members, I decided not to take Dutch anymore....no amount of fun playtime was worth damaging Dutch's laid back, fun loving nature.
I did try a couple of smaller play dates with another couple of boxers that I had met there, but Dexter started to constantly hump Dutch....and I do mean constantly, and that would set the other boxer on edge which was starting to cause some issues and minor fights, so I quit that too. :(
I make sure Dutch gets to go to his daycare once a week because he has a great playgroup that he plays with and loves, and I also make sure to take him back home to mom and dads as often as i can, were he plays with Molly and Blaze (ma and pa's two boxers).
I still miss watching him play and run with other dogs at the park, and how exhausted he was when we left.....but for me, its just not worth the risk.