Here are a couple of inexpensive places to grab a bite:

El Zaziummm (Mexican Food)

The menu is a creative mix of Mexican-Californian. The decor is recycled from anything and everything; you can dine in a carriage, sitting on the floor as arabs or even around a sand filled bathtub while you enjoy growing plants in washroom sinks plastered to the walls... quite eclectic indeed, made with anything you can find on a beach (beers cans, condoms, postcard, sand, etc) There are sometimes people doing tarot, mariachis. The servings are gargantuan, so much there are no desserts at all, none what so ever... Where you should find the dessert section on the menu it reads: "desserts : unbutton your pants instead!" ...and that's what you'll probably do after a "Monster": Le Monstre (so huge that if you eat all the plate,  'J'ai mangé le Monstre' which means 'I ate the Monster') the biggest hamburger you've ever seen, to those who dare and succeed, a 10% rebate on your bill and an "I ate the Monster" t-shirt.

Hamburger Mexicali, Fajitas, Hot dog Hollywood (bacon, merguez, cheese, mustard, tomatoes, lettuce with fries) ,1276 Laurier E., 598-0344; 4525 du Parc, 499-3675; 51 Roy, 844-0893). All on the Plateau Mont-Royal.

 For quick crepes, there is a place called La Crêpe on the corner of Rue Shebrook and Rue University. It's a small mom and pop place and serves very good crepes. They only have a couple of tables and a couple on the sidewalk, so don't bet on getting a place to sit down.