On the same trip, I was on a train from Italy to France. In my car was a French woman living in England, and an Italian woman. They were practicing on each other so the Italian would talk to the French woman in French, and she'd reply in Italian. This went on for some time. As we prepared to depart the train, the woman's child and husband joined her. I talked to the French woman's husband for 5 minutes or so. Eventually he asked me where I lived and I told him I was from California but studying in France. He turned out to be British, and switched to English and said "oh, well then I guess we can just speak in English then."
I'm sure our French pronunciation wouldn't have fooled a native, but it was good enough for a couple of foreigners.