I walked from Toulouse to the Somport pass in 2005 along with a monolingual Ozite (hi! Janet!)—she found the French hospitable and happy to jump hoops to somehow assist us- - they seemed to find it a source of delight to help out an Australian (and a Canadian!). Even so, my ability to chat away merrily in French was very helpful in matters of detail and just to socialize with people. Local people are very sociable and friendly, and treat cycling and hiking pilgrims with respect and hospitality—the greater your ability to connect with them, the more you will enjoy yourself.
Every tourisme office in each town or village had English-speaking staff, who were cheerfully helping out with information, reservations at inns etc. I keep hearing horror stories of Parisians furious at anyone trying out their basic French but I did not see this at all on the Camino from Toulouse to Spain. While I would urge prospective pilgrims to have enough French to find a place to stay, follow basic directions, and get some food, and carry on a basic conversation, it can be managed without. Remember to smile, be grateful for assistance, and enjoy the walk.