Visit the City of Portland’s Leaf Day website for information:
The city does not provide Leaf Day No Parking signs for most streets, nor will it ticket or tow cars that block street cleaning trucks (except on designated streets). It does provide a No Parking template you can print out and use to notify neighbors and other people who might park on your street on Leaf Day.
You can find a 2018 Leaf Day No Parking template at the Leaf Day website. (Save and reuse your signs next year. You can tape or write over the 2018 and write in a new date in 2019.)
(On my block we printed out and laminated enlarged copies of the template a couple of years ago and set them out (taped or tacked to cones, sawhorses, etc.) first thing in the morning of our scheduled street cleaning day.)
If you want to ask your City of Portland elected officials to create a regular street cleaning program or provide better Leaf Day No Parking options, not just a once a year program or a template, here are some cities with a variety of regular street cleaning programs that may serve as possible models for Portland. These programs are funded in a variety of ways:
Oakland, CA: https://www.oaklandca.gov/topics/street-sweeping