We are very used to sitting down at a restaurant in the U.S. and without asking if they take credit cards, order and consume. This can be a bad habit in France. Last year we found out the hard way, some restaurants only accept "Paiement Cheque our Especes" meaning in cash or by check.
http://www.northofandorra.blogspot.fr/2011/06/where-carte-bancaire-is-not-welcome.html
We ran into trouble again yesterday in Foix. Luckily, yesterday, the bank was just around the corner.