Some of you (maybe) expect Montréal to be a sort of Paris in North America, and it kind of is. There will be streets that look like they could be in Paris, but in general you'll be seeing a standard Canadian city where people speak French and the signs are in French too. There is more urban decay, the buildings are less grand, and the French accent is a little off—and the words are not quite the same in some cases.
But if you’re an American (or Brit or Aussie) coming to Montréal, there is some good news: Everyone seems to speak English, and English menus seem to be available in all restaunrants. Now, it’s important to remember that Québec is very proud (/ touchy) about French, so it would help if you tried at least a little to speak the language. I think it doesn’t take much. What I tried—and it seemed to work—was when I first encountered someone I would be talking to, I would say “bonjour!” in a jaunty tone and then segue into English. If I threw in some “merci”s and “au revoir”s, everything seemed to go smoothly. If you can do better than that, I’m guessing you'll do even better.
One word, though, of warning. Even though the Québecois accents are very nice, just as French accents are, when people switch to English, they sound a little bit like they're from Brooklyn. It’s a very flat American accent, which is quite unexpected.