That was exactly my wife’s and my experience when we were in Montreal for the F1 race a number of years ago.
Store clerks, waiters, taxi drivers, etc., would all start out speaking French to us, but as soon as they noticed our blank stares or heard us say “We’re from the U.S., sorry, but we don’t speak French”, they would switch to near-perfect English - and not one of them seemed to resent “having” to do it, either.