There isn't an official Urban Sketchers International group in Quebec City, but there is an active and fun group of people who get together and sketch all over the city and the region.
Your best bet for connecting is to check out the following:
1. Croquistes de Quebec
2. Collectif des Ateliers Libres en Arts Visuels de Québec
There is a lot of cross-over between these groups, and in both, there are people who speak English, French, and a number of other languages.