That is exactly the effect described by the GP: People appreciate you trying to speak French and help you out in whatever way they can, in this case by switchin

That is exactly the effect described by the GP: People appreciate you trying to speak French and help you out in whatever way they can, in this case by switching to English. The point is for you to give a decent first impression by doing some work and at least attempting to communicate in French rather than expecting them to speak English from the start.