TL;DR: You can still get by as a traveler in France with only English, but not without being polite and gracious.

As an updated answer to this question I can say that the previous answers still apply in 2018. I recently moved to Paris and found that while many French have difficulty understanding English (especially when spoken with a Southern drawl) or feign ignorance to avoid yet another tourist question, the vast majority of Parisians I have met have tried to accommodate my family and I. Even if conversation devolves to apologetic shrugs and hand waving, we have managed to order food, arrange hotels, navigate the metro, etc.

As others have said, the key appears to be to at least *attempt* to speak a little French, even if it's as simple as *bonjour* (pronounced bohn joor), *merci* (mehr-see), and *au revoir* (ah-voiah).

To help Americans get past the cultural wall, note that as children we Americans are taught to say "Please" and "Thank you" any time we ask for something. Similarly, the French are taught to say "Bonjour" when arriving at someone's house and "Au revoir" when leaving. Using those two words alone *everywhere* has gotten my family past the vast majority of the disdain for tourists we have seen others suffer.

Another tip for those learning French outside of France is to simply repeat whatever you hear the French say. It sounds silly, but it helps immensely with pronunciation which is quite difficult for anglophones (English speakers). Many thanks to the French taxi driver living near CDG airport for this tip.

Lastly, a caveat: If you are **planning on *moving*** to France, **learn at least passable French ahead of time**. Memrise, Babble, and a host of other apps are available if you can't afford classes. Due to timing of a series of unfortunate events, we were not able to do this and I can say that attempting to get Internet, a place to live, et cetera, in France without speaking French (or without a translator) is extremely difficult. To get internet, you need a cellphone account. To get a cellphone account you need a recent electric bill and a bank account. The electric company is notoriously allergic to English (our landlady was kind enough to handle setting up that account). To get a bank account you need a physical address and either the ability to speak French or a translator. French laws require the person signing a bank account to understand what they are signing. This is a good protection for those signatories, but does create the language barrier as most bank branches do not keep a translator on staff. We visited no less than seven different banks in Paris before finding one which had a person on staff who spoke enough English to communicate effectively with us and knew how to print out the forms in English for us to sign. Persistence helps too. But don't expect any of this paragraph to happen in August, when many French and most Parisians go elsewhere for vacation to escape the heat. Our account was on hold for two weeks due to that tip.