The short answer
No, you don't need French for a normal visit. The riads, the main sights and the main souks work in English. French does open more of the city, though: menus in neighbourhood restaurants, chats with riad owners, directions, taxi fares and anything outside the tourist core. Even a few French phrases make a real difference.
In more detail
French has been part of daily life in Morocco since the Protectorate years (1912 to 1956). It is still the language of road signs, business, many menus and most of the new town of Gueliz and Hivernage.
A handful of phrases cover most situations: 'bonjour', 'merci', 'l'addition, s'il vous plaît' for the bill, 'où est...?' for directions and 'combien?' for how much. Shopkeepers often switch to French when you open in it, and that can be easier than English for both of you.
If you speak neither French nor Arabic, don't worry. Mix English, a few words of Darija and gestures, and you will be fine. The effort to greet people in their language counts for more than accuracy.
Good to know
- Bonjour / bonsoir: good day / good evening.
- L'addition, s'il vous plaît: the bill, please.
- C'est trop cher: it's too expensive.
- Parlez-vous anglais?: do you speak English?