Thanks very much for the replies!
I figure Les Plaines and the walled city will be packed, but I just wanted to get a sense of how much the rest of the city is affected. My usual plan in QC is to hit up Au Bonnet d'Ane for dinner my first night, and I wasn't sure if the entire Faubourg would be unusually crowded or something.
I'm obviously looking forward to checking out the festivities! Should be a good time.