...If you do fly into Bellingham and feel that you have to start your ride in Canada you can do that one of three different ways... 2. Ride to the border at Blaine, continue on to Tsawwassen, catch the ferry to Swartz Bay and take the very nice bike route, the Lochside Trail, to downtown Victoria where you can take a ferry across to Port Townsend and start the ride south. 3. Bike SW to Anacortes and catch a ferry to Sidney on Vancouver Island and then take the Lochside Trail to Victoria.
These are two great suggestions. The ride on Vancouver Island is very nice, and Victoria is cool. Either the Tsawassen ferry or the Anacortes ferry is going to put you at the north end of the Lochside Trail (the Vancouver Island terminals are less than 5 miles apart.) I'd probably choose the Anacortes option as Anacortes/Fidalgo Island is cool, and you could stop at one or more of the San Juan Islands on your way. (Salt Spring Island would also be a worthy side trip.) An added bonus side trip would be riding the Galloping Goose Trail from Victoria out to Sooke or beyond and camping out there. Either option would be easier and more pleasant than getting through Vancouver suburbia (though you may see a little of that on the way to the Tsawassen ferry terminal.)
One note: the ferry from Victoria (Black Ball/MV Coho) lands at Port Angeles, not Townsend. It's a day ride between the two, much of it on the Olympic Discovery Trail.