I've stayed at bed and breakfasts a couple of times in Montreal and found
them quite comfortable and reasonably priced (especially because of the
favorable exchange rate). I stayed at B&Bs in the Downtown B&B Network. It
used to have a Web page, although now it seems to be down for some reason.
But I'm pretty sure you can find a phone number via directory assistance,
or in a travel guide. Most of these B&Bs are in the neighborhood near
Square St. Louis, a lovely park on rue St. Denis, a short walk from the
Latin Quarter and from rue St. Laurent (aka the Main).
If you go to Montreal in the next few weeks or months, be prepared for cold weather. But there are many things to do inside, including visiting the Museum of Fine Arts, the Architecture Museum, the department stores along rue St. Catherine downtown, and numerous restaurants.
I can heartily recommend L'Express on rue St. Denis, which is very popular but also reasonably priced. I also found a great little bar on rue Roy Est called Else's.
Enjoy your trip.
Evan in DC