You need to find an entrance with a booth, though. Many subway entrances don’t have that (most, if not all, probably have at least one entrance with a booth but not even sure if that is true anymore.

Don’t Presto cards still cost to get one - before you can even add value (used to be $5 per card, not sure if that has changed - probably up)? Especially in that case not worth it for visitors. And unlike other systems like, say, NY or Chicago, you can’t use a single card to pay fares for multiple riders at a time - so if you have more than 1 traveler, each needs their own card. If this is a one-time visitor, or very occasional - not worth getting the card. I like the systems that have the option of a transit card - but also where you can tap in with an NFC card / device (ApplePay, etc.) like in NYC or Singapore.