FYI, there are extremely few "French guys" living in Montreal... probably way below 1% of Montreal's population. The main two groups by far are French-speaking Canadians and English-speaking Canadians.
The Montreal crowd has unfortunately left this forum
en masse for greener pastures. Go to mtlurb.com, you'll reach a LOT more Montrealers that way and they'll be glad to give you way more details than I could.
Here's what I can tell you:
1) It's definitely feasible to find work there even though you speak only English, especially a "cheap labor" part-time student-type job (I gather from your post that this is what you'll be looking for).
2) Rents go down as you move out of the center... depends on how high are your standards and how much you want to spend to be downtown. Cost of living is cheaper than Toronto. If you live on the island, your car is going to be a PITA more than an asset (IMHO).
I would personally prefer living on the South Shore (the subway goes there) and leave my car there... your car will be very useful if you want to explore the area (I would obviously suggest that at some point you visit the Eastern Townships in your free time
and for that your car will be very handy) but it's likely to be quite useless for going around Montreal compared to mass transit for your commute.
Rents are cheaper on the South Shore, it's still relatively close to downtown by subway or bus, and it's going to be easy to park your car...