Do I have to be able to speak French ?
A knowledge of French will enable you to benefit more fully from your stay and to get more out of life in France. Learning the language will also help you with practical matters such as buying groceries, understanding directions and instructions, paying bills, etc. If your French isn't as good as you'd like, take some courses in France or in your home country.
But even if your French isn't very fluent, you can still fulfill your dream of studying in France by enrolling in a program taught in English. Here's a list of such programs, 600 and counting: http://www.campusfrance.org/fria/taughtie/index.html#app=8d6&b966-si=0.