I was just there last month and I didn't find the language barrier to be much of a problem. I think as long as you're not having a long, complex conversation with a cast member, you're fine. The only place I had an issue at all was at a counter service restaurant where the cashier kept thinking I was saying "fries" when I was actually saying "rice".
Just remember though, in France, the greeting is very important in french manners, so before you say anything, even in english, always precede it with saying "Bonjour!".
Also, not all of the rides say "Exit" in english, so make sure you know that "Sortie" means Exit.
Make sure you see "Captain EO" in 3D! It's the original from the 80s and it's completely in English!