I'm from Montreal, I can help you a bit. It depends what you want to do.
If you like sightseeing, then you should visit the old Montreal, Saint-Joseph's Oratory, Notre-Dame basilica and a bunch of museum. And the night view from Mont-Royal is not bad.
If you are more into nightlife, you can find a bunch of bars and clubs around Crescent street in downtown, or Saint-Laurent street (North of Sherbrooke)
If you wanna do some shopping (which I don't think you find cheaper stuffs than the states
) you have the underground mall in downtown and also there's this sector they call Plateau Mont-Royal, where you can find a bunch of interesting little stores.
If you wanna eat, Montreal IS the place. Although not everything is good, but you have tons of restaurant from different country. You have Chinatown if you feel like some Asian food, if you want a fancy restaurant, I'll say go look around in old Montreal, it is where they usually are.
As for staying, I'll suggest you stay near downtown and you should take the subway here (We call it Metro), there's a bunch of construction here and so it is sometimes faster to travel in subway than by car.
Aight, that's all i can think of for now, I'll add more if I can think of something else lol