Maybe his snake needs exercise
I wouldn't personally take a snake to a park unless there was some kind of snake meet. I do take one or the other to the pet store on the rare day. It's a really good feeling when someone takes an interest in the snake, especially children.
It's not illegal, and if you don't take our advice, just be sure to be courteous to other people and don't ever walk towards someone who is visually terrified. You and I know that you're more likely to get bit by a random dog at the park, but someone who has a fear of snakes doesn't care and probably won't listen or care how friendly your snake may be.
