On the face of it, in any company, the correct language to use for code is the official internal language of the company: the same language you use for inter-departmental communications.
This might well be English, but if it isn't then it could be because you have non-fluent-English-speakers working in the company, perhaps as programmers, who might need to understand your code. More importantly they need to clearly document and comment the code they write. In a language they don't have fluently this will result in some confusing comments, although code review would sort that out. Those people will of course speak your official language, so it may be easier to stick with it.
But that's just the official line. Even if your company uses French internally, and makes fluent French but not fluent English a condition for all employees, programmers are more likely than the average employee to speak good English. And some day you will hire a hot-shot contractor who doesn't speak French. Chances are this contractor speaks English, perhaps exclusively. So code written in non-fluent English is probably more useful to him than code written in French, and you're paying him considerably more per hour than anyone else in the organization.
I suppose what I'm saying sort of implies that every company should mandate English as an internal language, and require/teach all employees, especially coders, fluent English. But then I'm an English-speaker who on a good day can maybe get the gist of a newspaper in French, a child's book in German, and nothing in any other language. So I'm hardly entitled to an opinion, and I'm inclined to suggest that if anyone in the team is less than fluent in English, you should muddle through in whatever language the team knows best, and be prepared to translate later if you hit problems. I base this on the simple fact that if I was required to write code in any language other than English, I'd do a terrible job of it. So I assume the same is true of the (very small) proportion of French programmers whose English is no better than my French.
I have encountered comments written in French before, in an English code base. The author was French, and presumably wasn't paying attention when he wrote them. I understood them, but I was glad that the Swedish and Dutch guys never did the same thing. It's probably most important to pick a language that everyone can use, because a mix of languages is probably worse than a single language that everyone knows they should improve if it's not their native.