There are a ton of restaurants around McGill and throughout Montréal that are both cheap and good. Dining out in Montréal can basically be broken into two categories: fast food and not fast food. Fast food here is taken seriously, with eateries offering falafel, poutine, pizza, burgers and fries, barbeque chicken, or all of the above. Shish Taouk sells falafels for cheap, and there are 99 cent pizza parlors every block or so. After dancing all night, poutine is better than any drug. These places are great for a student who is watching their budget, but not their weight. For anyone who likes all things artery-clogging, the fast food joints of Montréal are greasy, cheap, and guiltily good.
On the other hand, if what you're looking for is a nice but affordable dinner out, there are still plenty of options. All along Prince Arthur there are BYOB restaurants that serve every kind of cuisine, from continental to Cambodian. BYOB refers to bringing either your own wine or beer (no hard liquor) bottle to have with the dinner that you purchase there. This cuts down on the overall cost of your meal. Really, one of the nicest things about not having a legal limit is being able to have a social drink with your meal. The main thing about cuisine in Montréal is the variety of cultures that it represents. Montréal is an immigrant's city, and the food consumed here reflects that. Shwarma is as popular as a hamburger, and a bowl of Tonkinese soup is preferred to plain chicken noodle to warm up in the cold winter.