You'll definitely need a work visa. The thing is, if you want to practice your French in the country, then you'd need to go somewhere like Quebec. Canada may be bilingual in terms of it's primary language, but the majority of people speak English primarily. Quebec however would be more likely to have French speaking. The other thing is, the French spoken in Canada is not exactly the same as the French that is spoken in France. While there aren't major differences, there is something that's considered Quebecois French.
Either way, you'd best talk to the people in charge of you going there. It's a huge country, so it really depends on where you want to go.