[Amgine]

Actually, I wouldn't suggest leaving a boat for any amount of time at anchor without someone aboard. I don't know of any safe anchorages near Vancouver where you could do that, actually.

Probably the least expensive, but not very convenient, tie-up option would be Shelter Island Marina in the lower arm of the Fraser River. Because it is so far up the river you will spend a number of hours motoring against the current: you will seriously want to make sure you are on a rising tide. It is possible to bus from the marina to the train station in downtown; it'll cost $5.50, and may involve a couple of transfers. Otherwise you could just call a cab. If you do decide to try Shelter Island DO NOT try to enter the marina between Lion and Don islands: you will run aground. Go upstream of Don Island and carefully approach, watching the depth sounder very closely because it's been a while since they've dredged up there.

Other options include Lynnwood or Mosquito Creek marinas, on the north shore, or better yet Gibson's Landing (which will involve catching a ferry to Horshoe Bay and a bus or cab to the trainstation from there.) Gibson's Landing would be the best choice, imo, being another day up the coast from from Vancouver, but will take the same amount of time to get to as Vancouver from Seattle. It's possible to get from Point Roberts to Gibson's in a single day on my little boat, but it's a very looong day.