Upload & Sell: On
For me, it's always $US, unless explicily stated otherwise. Same as on eBay.com, where it's explicitly $US.
If I get a CA buyer, I'll offer to do the deal in $CA, based on current www.xe.com rates to get from the $US price to $CA, in which case, we both save on exchange charges. If the CA buyer doesn't want to go for the $CA equivalency, or doesn't answer in a reasonable time, then I consummate in $US.