From the junction to the coast via the PNT is something on the order of 600 miles. While it is true that after you leave the Mount Baker area (about 10 days or so) you reach low elevations, it will really suck in October. It will be cold and rainy and you’ll be bushwhacking at times, which means that you’ll be soaked. And you won’t have any views. The island hopping stretch might be pleasant, but you’re going to be wet and cold and miserable. And then you get to cross the Olympics, where you’ll go back up to over 6000 feet. The Olympics are the first thing that storms hit when they come off the ocean. The weather is worse, the winds higher, the air colder. You don’t want to be up there without the right gear in bad weather, and just about every day after mid October will be nasty.
Of course, you could get lucky. Or, it could be like this year, where after about September 15, the weather was awful. So, if you get to Manning around mid August, you’ve got a shot. Otherwise, catch the bus to Vancouver and then hop the ferry to Victoria (its on Vancouver Island). Hang out, then catch the ferry to Port Angeles (in Washington, on the Olympic Peninsula). Hang out, then catch another ferry to Seattle.
Suge