I don't think anyone should freak out at you at all. But, I wouldn't do it. A rule at both dog parks I go to is to remove your dogs leash in the entrace area between 2 gates. Not only will other dogs pick on your dog much more with him being on a leash, your dog is much more prone to get defensive. On leash, HE is attached to YOU, and he most likely feels the need to protect you. He also can't get away if he only has 6 feet to run and a hyper puppy is barreling into him. Not only that, but a dog's posture when he's straining on-leash (even if he means to be friendly) can appear rigid and aggressive and could start a fight out of nothing. At our Obedience classes, we couldn't allow our dogs to even sniff each other on-leash, but they were allowed to play off-leash in a fenced area.

Gonzo is much more snarky with other dogs on-leash than he is off. If he's off, he'll just ignore an annoying dog... if he's on, he has no escape from them!! Which, in turn, can lead to a tiff.