When it snows in Mountainside, N.J., families often set off for the bunny hill in Echo Lake Park with their sleds and inflatable tubes. In the summer, they may spend their days at the community pool. And on Halloween, everyone heads to Old Tote Road, where children from various towns gather to trick-or-treat.

It was during one of those Halloween nights a couple of years ago that Ricardo Costa, who had been invited with his family by a friend in Mountainside, decided the borough was where he wanted to live.

“It reminded me of one of those old movies, where everybody’s out on the street and it’s safe and friendly, and everyone’s having fun — the kids and the adults,” said Mr. Costa, 40, a sales director for Herman Miller furniture, who was living in Rahway, N.J., at the time.