Hi there… I agree with a couple of comments already given to you… I lived 3 years in Montreal, and I was perfectly comfortable speaking either language. There is like, no rule as to how people will react to your request on practicing only your French.
I can tell you though there are “quartiers” where most of the French speaking people live (for instance Rosemont, where I was living.)
If you want to squeeze the best of a multicultural place to live, and enrich your life to the fullest, Montreal is the place to go.
The Quebecois are very warm and nice people (both French and English speakers). It is rare to find an English speaker that won’t indulge in your request to just practice your French (if they do speak the language).
So, in a nutshell, I would suggest you find the coolest place to live. Don’t worry about the language.
If you ask me, best places to live are Montreal and Québec City (culturally speaking). Sherbrooke is cool if you want to just chill. And Gaspesie if you want to freeze your butt off while enjoying the most amazing nature ever.
Have a great time in Quebec!!