The official language of the province of Quebec is French, but in Montreal, English is an official language, too. Quebec has a huge indigenous presence as well, so there are significant numbers of people who speak Algonquin, Micmac, Mohawk and Cree. Additionally, there are large immigrant communities here, and in particular Montreal has large Arabic-speaking and Spanish-speaking populations.
The Canadian dollar is used, which is equivalent to about 75 cents in the U.S.
A bottle of water costs between two and four dollars, depending on how fancy the packaging is!
I used to be a nanny for a family in Montreal, and I went out for breakfast with them for one of the kid's birthdays. The restaurant does "Disco Déjeuner" on the weekends, or "Disco Breakfast," so while we ate our pancakes and eggs, they were playing disco music!