French does not rank among the top 15 languages spoken in Toronto and there are only around 7,000 French speakers in the Greater Toronto Area (about 0.1% of the population), so the language is fairly useless unless you specifically plan to work in a French restaurant there.
Montreal, on the other hand, is an entirely different story. Although the population is multi-ethnic and largely bilingual, French is the official language and is a requirement if you want to work in the service industry (customer service). Having said that, there are probably more than a hundred restaurants in the city where English is the language spoken in the kitchen, so the lack of French-speaking skills whould not necessarily prevent you from finding a job. You have to ask yourself a fundamental question however: why would I want to live in Montreal if I don't speak the language or intend to learn it? When in Rome...
By the way, I was in Melbourne last month and absolutely loved it! I guess the grass always seems to be greener on the neighbour's lawn