Laval, within a 20 minute commute from one of the subways that will get you downtown in another 20 (several within walking distance).
Deux-Montagne, 10 minute commute to train station, 30 minute to downtown train station.
Longueil, either buses straight to downtown (reserved lane), or bus to the Longueil metro station.
If you want to drive, I'm counting 10,145 4BR+ houses within 50km of Montreal, but I wouldn't do that. The REM electric train will improve access to downtown for the western part of the south shore, west island, and northwest shore (deux-montagnes).
If you prefer city life, there's 8,438 2BR+ condos for less than 400k within walking distance of the subway system (68 stations).
I dig Laval because I work in the east end of Montreal and can get there with no traffic delays, and I can take my road bike and bike for 60km with just a few stops.