French is the working language in Fontaines-Saint-Martin, and while English is sometimes understood in nearby Lyon, the village itself runs on standard French. A basic greeting of 'Bonjour' before any interaction is not optional courtesy — it is expected in shops, the mairie, on buses, and at any local table. Visitors who skip this step often receive curt service or a polite correction.
The local register is standard Lyonnais French with no significant regional patois spoken today. Because the commune is small and residential, you will encounter shopkeepers, mairie staff, and TCL bus drivers who appreciate effort over perfection. Knowing a few set phrases for the bakery, the Lyon-bound bus, and emergencies will make daily logistics much smoother.