It completely depends on the office but B1 or B2 should be enough. I came in with B1. If you don't have any knowledge of French, I would suggest you to wait, however, to each their own. If it's not your intention to settle in Quebec then a basic level of French will suffice to pass the interview (you will have one, have no doubt on that) and as it was mentioned, it can take almost a year to get one, but if you intend to stay and live in Quebec, even if it's Montreal, you will need to have an advanced level of French, Quebec French isn't the same as the one you learn in the French Alliance, so it's harder to understand and even if you're in an advanced level, you will initially have trouble understanding people here. So my advice is to wait to learn some french and then apply, but it's up to you.