LS and Fatum,
Thanks for all the information and advice. Unfortunately, we'll only be in Vancouver for 2 days and 1 night, so we'll really only have time to hang around Vancouver proper and the Richmond district where the "new" Chinatown is located.
Given Vancouver's proximity to Seattle, I would not be surprised at all that US currency is readily accepted there. As Fatum has mentioned, it's just a matter of how much they are going to "profit" from the exchange rate. Just to be on the safe side, I'll be bringing a small amount of Canadian currency along (I was able to net a reasonably favourable exchange rate at the local branch of Well Fargo, with whom I do business).
I'll be bringing my laptop and the hotels in Seattle and Vancouver have free wi-fi, so I'll be able to keep in touch with you guys during the trip!