I live in Québec city, but I don't know it that much. What I know is that there is a lot of motels on Wilfrid-Hamel blvd, which is the street where the Colisée Pepsi is.
Here are some hotels I know, who are not necessarily on Hamel, but are affordable, to my knowledge:
http://www.abitation.com/en/index_en.html
http://www.hotellecofortelquebec.com/introang.html
http://www.chateaurepotel.com/
In any case, this Yellow Pages site might help you:
http://www.yellowpages.ca/search/?stype=si&src=&what=Hotels&where=Quebec&x=0&y=0
And this one too, it has info about other stuff in Québec city:
http://www.quebecplus.ca/feature/english/55/
This is the website of the public transportation system:
http://www.rtcquebec.ca
It's only in French. From what I see, the interesting lines would be the 12, which would take you from the Old town to the Colisée in roughly 1/2 an hour; the 4, with a similar course. In any case, you can always inquire at the place you book for the convenient bus rides.
From what I see, if you're on foot, the downtown hotels would be more advantageous, because that's where the buses depart from. If you have a car, Wilfrid-Hamel blvd surely will yield affordable places. Forget the Old town if you're on a budget: even the B&Bs are probably high priced. The hotels on Laurier blvd could be reasonbly priced at that time of the year, but I think the public transportation would not be exactly practical. The problem stems from the fact that most lines are east-west, so moving south-north is always a problem. But like I said, I'm not highly cognizant in the bus system.
If there's any question I
can answer, I'll be happy to do so!