Vancouver, BC to Bellingham, WA via Richmond, Surrey, Blaine, Ferndale
These are just notes...need to write up a detailed description but hopefully these will help in your planning!
There is a detailed bike route map of the vancouver area (all the way to the border) at http://www.translink.ca/en/Getting-Around/Cycling/Cycling-Maps.aspx
South from Vancouver, the easiest way is take the Cambie St bridge south from downtown and then follow the Ontario bikeroute (just west of Cambie) all the way to the north arm of the Fraser River and then go over the bike bridge on the Skytrain bridge.
Turn left off the bridge and follow River Rd east.
From there you need to decide how you want to cross the south arm of the Fraser River from Richmond into Delta or Surrey. I prefer the route that roughly parallels Highway 99 but the disadvantage is that there are no bicycles allowed (and definitely not possible) in the tunnel that goes under the river. There is a free bike shuttle that runs more or less hourly, see http://www.th.gov.bc.ca/popular-topics/driver_info/route-info/massey/massey.htm for schedules. Or all the buses traveling through the tunnel have bike racks as well.
To get to the tunnel, you would turn right at Shell Rd and continue south on the road and on the Shell Road bike path all the way through Richmond until Steveston Rd and then find the shuttle pick up point on your map. From the shuttle drop off you'll need to head east, River Rd in Delta is a good choice although a little north as well.
If you don't want to take the tunnel, your would continue along River Rd east instead of turning at Shell. About 10km further east until you see signs for the Alex Fraser Bridge which has a narrow bike path (crossing Annacis Island) which you can cross into Surrey/Delta.
Either way you can then head south through Surrey to the border; I've never found a nice route through Surrey. They're all ugly. Either border crossing, at hwy 99 or hwy 15 is fine.
From the border, Portal way is direct but not the most scenic as it's close to the freeway. Make your way towards Vista Dr then Marine Dr into Bellingham. If heading south to Seattle I usually break the trip in Bellingham which is a nice university town.