hi! you can go downtown montreal on ste-catherine and st-denis streets, there's a good night life, during the day there's a lots of boutics and shopping center. i suggest you to go on Mont-Royal is a little mountain in the middle of the city and every sunday there's a gattering called "tamtam" this really cool, it starts in the after noon. You also have the old port which there's a lots of activities to do.
and there's a lots of festivals in montreal like the jazz festival, festival just for laugh, and francofolies, etc...
but this is all in the summer... winter time is little quiet.
you also have the biodôme, jardin botanique, and la ronde which is an attrations park...
Enjoy!