Post Cruise Quebec City Luggage ?

[dsgtwife]

I read on the Quebec City port site that you can leave your luggage for $4. each piece when you are disembarking for tours, but it really doesn't say if you can drop your luggage off that morning if you are planning on leaving on a cruise out of Quebec City at 8:00 p.m. We are planning on arriving Sept. 27, 2012 and spending a day in a rental car, turning it in early on the 28th and dropping off the luggage at port, then touring the old town until time to board. Is this possible? And what time does NCL Dawn start boarding for an 8:00 p.m. sail time? Thanks!