Several times when arriving at "French-only" airfields I've called up with "XXX bonjour" and my callsign in standard phonetics (with a French bias - "Yonkee" rather than "Yankee" etc).
As often as not, they reply in English. Usually there's no other traffic about anyway.
The only really scary moment was going into Toussus, speaking English to the Tower: I was on final to 07 right and an aircraft shot across in front of me a couple of hundred yards ahead and a few feet lower, and turned final for 07 left. That really shook me; when I told the controller about it, he explained that English-speakers were being given 07 right, and French speakers 07 left. Scary!