I most always drive but took Quick Shuttle once. Avis, Budget and National- all of which I have used offer one way Seatac- downtown Vancouver without additional drop off charges - about $75. I usually stay in Bellingham the night before- loads of cheap lodgings opportunities- Motel 6 about $40, then it is only an hour drive to Canada Place. The train leaves downtown Seattle about 7am, a cab would be required airport to downtown Seattle and downtown Vancouver to Canada Place. Only 1 round trip train per day.