People can't live in vans parked in driveways. The City of Portland is who you should call... it's confidential and they can enforce codes specific to your concern: 503-823-2633 (I've called them a few times due to my neighbor not having garbage service and piling bags in his driveway).

Yup. Let the city handle it, the complaint can't be traced to you. They will inform your neighbor of their rights and obligations.