I would agree that if you don't speak french, I would stick to Montreal itself and not Laval. Not that you wouldn't get by, but more people will be english on the island. That and Laval is a suburb like you would find in any other city. Sure it happens to be very close to downtown and all the advantages listed above, but if you're gonna go to the trouble of moving here, might as well go all the way
The west island area will be 90% english, but its basically just an english version of Laval.
Downtown is closer to 50/50. Without knowing you at all or what you're looking for, in general I would suggest downtown or old port. And if the whole nightlife scene is what you're after, none of the other areas compare, at all.