Most visitors will tell you: "yes, they will speak English, no problem."
I personally had quite mixed experiences.
It's normally fine for standard stuff like restaurant ordering or paying in a store. However, when it's about more complicated things - heaven forbid I have some dietary requirements - it gets a little more complicated. Normally you're able to work around that though.
Lately it happened to me more and more often that as soon as there was a problem suddenly no English speaking CM was available or in some cases a CM who had at least tried to work with me before suddenly "unlearned" English and out of the blue told me in French he didn't understand me.
But I realize for my negative experiences there's 3 other reviews that will be extremely positive, so hopefully you will be fine.
Also the flags on the uniforms keep getting more sparse (or maybe I didn't see them in the winter clothing). I haven't noticed any for ages and got accustomed to asking "Is English okay?"