Hello Scott! Montreal in summer is really nice!!!There's the downtown on ste-catherine and st-denis streets where the night life is really cool, during the day there's a lots of boutics and shopping center. Lots of tourists like to go on Crescent street. I suggest you to go on the Mont-Royal, is a little mountain in the middle of the city and EVERY sunday there's a gattering called tam-tam its nice, you can relax in the grass and listen the tamtam, it starts in the after noon. You also have the old port which there's a lots of activities to do.
There's a lots of festivals: the jazz festival in july, festival just for laugh, and francofolies, etc...
You also have the biodôme, botanic garden, olympic stadium, and la ronde which is a big attrations park... Well let me know if you want more specific tips!
Enjoy!
Véronique