I would say this clinic is better than most, but I still ended up waiting a long time (more than 5 hours altogether).
I went in just before 8am (they open at 7am). The receptionist gave me a number. She didn't actually explain it to me at first, but you can call the number on the ticket and it will text you when your number is getting close. (I dont know why every clinic doesnt do this.) It cost $3 for this service but it seemed well worth it. I went to a coffee shop nearby to kill time. At about 10:35 I got a notice that they were a few people away so I came in. About 20 minutes later I saw the nurse. She told me to go back out and wait. At 1pm (an hour later), I was still waiting to see the doctor. So it's a good system in theory, but you should still be prepared to wait.
My suggestion is to wait until your number is very close. You don't want to miss your slot, but the nurse called people a few times if they weren't there so it seems like not a big deal. An even better idea is to show up at 7am or even before so you're the first one to be seen. It seems like the only way to save burning your whole day. Don't bother trying after 11, they will be full.
It makes me sad to say it, but this was still one of the better experiences I've had at a walk in clinic in Montreal. The receptists were nice. People were mostly fine about speaking English (it helps to try in French a little if you can). Would have been 5 stars if they hadn't called me in way too early.