It's okay, but you'll get a lot of *ssholes pretending they don't understand you when they do and some people like to f*ck with English peoples heads (harmlessly but annoyingly). But you can get along fine out there speaking English as most businesses, etc, have employees that speak both languages. There is a surprising amount of English speakers in Montreal.
It's actually quite an amazing place, but there are a lot of crazy people, party people, homeless people and drug addicts in a lot of areas. It's a party city, that's for sure. Can get a lot of good stuff out there, I won't lie.
Anyway I'm getting off topic. You'll do fine and you will eventually start to learn some French words and phrases the more you hear it. People are pretty cool about teaching you French out there.
I lived on the streets of Montreal and don't speak a lick of French, but did just fine.