Hi there,
I'm not in your subfield, but some rough ranking will go like this for bio / life sciences:
McGill (highly internationally ranked, new facilities, human genome project centre, highly competitive, R1)
UBC (highly ranked in Canada, strong in marine bio. R1 or R2 depending on program.)
Dal (stronger on botany, marine bio., etc. Not primarily a research school.)
I know less about McMaster and Western, except to say that their marquee programs are medicine and business, respectively. I'd class them similarly to Dal. It's a deeply flawed list, but for a US News-style ranking of Canadian universities, see Maclean's magazine.
Vancouver is currently the most expensive city to live in in Canada (Toronto follows pretty closely.) I'd recommend roommates. In Montreal, you can pay as little as $350 per month in a shared space in nice neighbourhoods that are a little trek from McGill. I paid between $400 and $500 in different shared places over the years. Also, student metropasses are reasonable (less than $40/ month), and the transit system is pretty good. French is helpful, but not mandatory, especially if you live closer to McGill. While there is an enormous underground shopping mall that connects a lot of downtown, you most definitely cannot spend most of the winter underground. In fact, the key to surviving the winter is to find something you like to do outdoors in the snow. Skiing is highly recommended. (I did my ugrad at McGill, and am now at Toronto). There are quite a few Americans.
As per careers, I'd say that applying to work with specific people, and letting that decide your institutions, is a good plan (or at least what I'm doing). Generally, if Americans have heard of a Canadian school, that school is McGill (though Toronto is in general a stronger school). So, if you're concerned with name recognition later on, that may be a factor (if you're planning to stay in academia, actual reputation is probably more important than name recognition).
Cheers,
gr