You are looking at a minimum of 30 minutes to get to those parking lots anytime you will need your car. The other issue is snow... Some of the lots will either be closed at night or your car will simply be surrounded by snow (the snow removal guys usually have "fun" burying cars that are in the way to teach the owners a lesson)...

You can probably find 10-15$ a day parking in the area around the Hyatt (south of Rene-Levesque)