Alternate Scenic Route to Anacortes
Portland to Centralia is a breeze.
If your destination is Anacortes for the San Juan ferry, you can take the scenic route and avoid urban traffic. About 30 miles north of Centralia you can take HWY 101 and follow signs to Port Townsend, a great historic waterfront destination in itself. The route takes you along the scenic Hood Canal and the base of the Olympic Mountains. You can take the ferry from Port Townsend to Coupeville and drive to Anacortes.
On the Port Townsend route, you will cross Deception Pass south of Anacortes, the gateway for boats to the San Juans. It is worth stopping to take a peek over the bridge. When the current is slack, it is a parade of boats, when the current is running it is an amazing sight of whirlpools and turbulent waters surrounded by rock cliffs, small rock islands and tall evergreens with a view of the San Juans to the West.
If you are taking an extra day, you can continue past Port Townsend on 101 to Port Angeles. The locals put a Clipper Creek CS-100 a couple blocks from the Black Ball ferry dock to Victoria, BC. The ferry's name is Coho and it lands in front the Provincial buildings and Empress Hotel in the heart of Victoria. In Victoria's northern suburb of Sydney, you can catch the WSF to the San Juans. Just don't forget your passport if you use this route!
These are some the most beautiful drives in the country. (I think it is THE most beautiful and that is why I can't move away!)
The only caveat is, when there are extreme tides, the Port Townsend/Coupeville ferry will cancel some runs while the tide is out a couple times a month. Warnings and dates are on the WSF website.
WSDOT - Ferries - Schedule: Summer 2014 Tidal Cancellations for Port Townsend / Coupeville
- - - Updated - - -
The ferries will still be on Summer schedule in September. That is prime season in the NW still. I'd be certain to get reservations on all the routes I mentioned, including the San Juan route.
Washington State Ferries Vehicle Reservations System (WSF VRS)
You might not get lucky making it to the Anacortes ferry by 2pm if you go through Tacoma and Seattle. Too many bottlenecks and incidents. There is no grace on weekends either when it comes to I-5. Traffic routinely doubles travel time. It routinely takes me 4 hours to do the drive from Centralia to Seattle.