It's a french thing. Once I literally was told that the cafe "is closed" because I dared to speak english. It was Carcasonne fortress, midday, middle of summer, with hundred other people being served. Don't hold your breath
That said it doesn't hurt for bonjour to be the first word out of your mouth. It is France and they speak French after all. The same goes for hello in every other language in every other country on earth as well.
source: American who has lived in France.
English is the 2nd language most people in the world knows so that's a natural language to use approaching people whose language you don't know.
English is not my native language. If someone visited my country I would expect them to speak to me in English, not learn my language unless they were going to settle here.