Firstly I'd suggest you look an an earlier answer to a very similar question: How to overcome the language barrier when visiting France and Spain?
Thinking of Paris specifically, you should find a lot of people who do speak at least some English, generally higher than in more rural parts of France. However, you'll also come across a lot more people who've got fed up of tourists who've not bothered to learn a single word of French...
So, I'd suggest you follow the advice in this answer, and learn some basic French! With even a few words you should find things go much easier. Without that, you'll mostly be fine, but may experience some hostility once or twice.