Hey Eeyoreland!
Couple of tips for you... the French are very pinickity about sitting in restaurants if you don't eat, especially videopolis if there is a show about to start, quite often I've had a french CM come up to me and shout a whole lot of french at me to my bafflement and just look blankly at me... so advice, try not to do that!
Other than the random french speil as I've mentioned above the language barrier is not a problem, all the cast members speak good english and most of them will be willing to have a conversation in it, but as MazdaUK said basic yes, no, thankyou, hello and goodbye are very much appreciated.
You also have to be prepared for the fact the french, and indeed some of the German do not que, especially when a character is about, they tend to bundle, which isnt so much fun! Parades are ok, the street fills up very quickly though so make sure to get your place early!
Don't go expecting WDW in Paris, because it's not, but it's a completely different experience and one that I would definately recommend!
Hope you have a great time!