I don't know what date you're looking at, which would help. But the only connection from the Coast STarlight (only train that runs between Santa Barbara and Seattle direct) is a bus that gets you into vancouver after midnight. I assume that's what you found for $106?

That wouldn't let you do any stopovers, which you were talking about. Also, the train ride from Seattle to Vancouver is one of the best in the country, so it would be a shame to sit on a bus for that.

Do you have any amtrak points? If so, the pdx-sea and sea-vac routes are great place to use them, as it's only 1000 points to redeem a coach (one-way) ticket on that route. If you're looking at this summer, there may be enough time to sign up for the Amtrak Chase credit card and earn some points you can redeem that way (I don't know what the current sign-up bonus is -- it was 10K when I did it a while back).

Unless you want to bus to Vancouver, you'll need to overnight in SEattle, as the only train to VAC leaves at 7-something in the morning.

Taking the advice of the above poster, I priced out a ticket from SBA-PDX (2 nights PDX), PDX-SEA (2 nights SEA), SEA-VAC for $153 in a coach seat, which seems like a good deal to me.