I grew up in Montreal and did my undergrad at McGill. It's an amazing city. Cheap as dirt to live and play and also really beautiful. The campus is right in the middle of the city, bars, major shoping. Sometimes I wish I'd never left.
Here is some info for you.
Public transport is very easy as is hailing a cab but if you live near the university you most likely wont need it. You can walk everywhere. A lot of students live in the McGill Ghetto area or the plateau. The more east you go the more french the city becomes.
Cell phone plans with data are expensive. Rogers and Telus are good. Bell is ok. That's the one draw back. Videotron is the biggest TV, Internet provider in Quebec. Be careful though because they charge you per kilobite after a certain amount of downloading/uploading.
Good luck!