I know because I got out this afternoon to that Shoppers and bought a Presto card, trying to be patient with the parking lot of cars filling all the streets between me and it. Had thought of going up to the one on Dupont, technically closer, but traffic is doubtless worse the farther east you go and Dupont drivers are murderous at the best of times. Anyway, it's done.
Tried to register the card at once- won't get fooled again- only to encounter the message
"If you purchased a PRESTO card at a Customer Service Outlet, you will need to wait up to 24 hours before creating a My PRESTO Account online." OK. So don't use the thing tomorrow, just in case; and hopefully I can still bicycle then.