Locals along the Camino are extremely friendly and will accommodate tourists and pilgrims with limited to no French. Of course, making the effort to learn a couple of phrases will go a long way!
Learn Some Basics
I suggest trying Duolingo, a free language-learning service for your browser or smart phone. They offer a ton of languages including French and you can begin your lessons at any level.
Reservation Email Template
Below is the template I used to make reservations with hostels along the route. I've placed the English translation in brackets alongside the French for your benefit.
Je suis un pèlerin sur Le Chemin Compostelle, et je voudrais faire une reservation pour le 29 Avril (I'm a pilgrim walking El Camino, and I'd like to make a reservation for the 29th of April). Une personne pour une nuit, avec le petit dejeuner, si possible (One person for one night, with breakfast, if possible).
Mon numero (My telephone number):
Je vous remercie! (Thank you!)
Words to Substitute:
-Are you a woman or a man? "Pèlerin" is masculine, "Pèlerine" is feminine.
-Want dinner AND breakfast? Replace "le petit dejeuner" (breakfast) with "demi-pension" (dinner and breakfast).
-Want dinner WITHOUT breakfast? Replace "le petit dejeuner" (breakfast) with "supper seulement" (only dinner).
Further information required:
This template will cover what most hosts require for a reservation (food preference, number of people, dates), but if they reply looking for more specific information, Google Translate is surprisingly accurate. For one-word translations, Word Reference is a great resource. Carrying a physical phrase book is just extra weight!