I’m from Montreal (though not lived there in nearly 15 years). Although I’m a French speaker, I have friends who relocated to Montreal from the UK, US and other English speaking countries. I’ve also emigrated to the UK and I’m now an expat in Asia, so I can see your question from a number of angles.
I think you can manage in MTL without any French at all, but you may find yourself slightly isolated. French speakers may also enquire (genuinely/forcefully depending on their political proclivities) why you don’t speak French; this is because of the province’s history, and as a newcomer you shouldn’t feel embarrassed, but I think it gets tiring after a while. Quebecers are very nosy.
Montreal has two English universities, English hospitals, English newspapers, theatres and so on, and most young people are bilingual to a degree. You won’t have difficulties being served in English in any store or restaurant. Several neighbourhoods/ arrondissements are majority English speaking (Westmount, NDG, Côte St-Luc, Côte des Neiges, and all of the West Island towns eg Beaconsfield, Kirkland, DDO etc).
Having said all this, it can be isolating to live somewhere where you don’t speak the language of the majority. Montreal is not an expat town, so it’s not like you’re moving to Dubai or Singapore where everyone is transient. Making friends is going to be more difficult because the locals already have their existing network of friends and family. Even if you join a local community club or group, odds are some of the socialising will be in French, so you may find yourself excluded from the conversation.
I’m sure you know that, but it’s also very, very cold. Brace yourself for a long winter and learn to love winter sports, shovelling snow of your car and taking 15 minutes to put extra layers on every time you go out.
Other than that, it’s a much more egalitarian society, no class system, less sexism. Unfortunately it’s also quite racist - the government is currently trying to pass a law banning headscarves (and all other religious signs, but the law is clearly targeting Muslim women.) It’s pretty appalling.
Oh and beware of the extremely complex street parking rules, and crumbling infrastructure (potholes everywhere). But glorious summers, very good food, generally good air quality, and lots of big parks.
You don’t say if you have children- French education is mandatory for all non Canadians (with very few exceptions), so if you have children they’d need to go to a French school, unless you go fully private for their entire education, which is not cheap, eg see here: www.lcc.ca/admissions/tuition-fees.