For the French, lunch is usually the main meal of the day and they spend 2 or 3 hours over it. Nearly everything except for cafés & restaurants closes between midday and 2 or 3pm, so be warned! The cheapest option is to take the 'menu', which is an appetiser, main, and dessert, with often a ‘pichet’ of wine as well. (If you want to see what we call a menu, ask for "la carte".) Baskets of French bread are plentiful and free, as are carafes of 'eau de robinet' (tap water). Mineral water is quite expensive. Be prepared to take time over your meal, as everything is prepared freshly. What can be annoying is waiting for 'l'addition' (the bill) -- nobody seems to want to take your money! I've found the best way to deal with it is to stand up as if you are leaving -- that usually works!
On the Cote d'Azur the fish is fresh and excellent. Try the mussels ('moules'), which are not huge like our NZ green-lipped mussels, but small and sweet. Salads are often just green salads, without any additions, but have the most wonderful dressings. And as Menton and Roquebrune are near the Italian border, pizzas and pastas are everywhere, and are really delicious. Another local dish that I found to be very good was 'souris d'agneau' -- literally ' mouse of lamb', i.e. a lamb shank. And 'creperies' (pancake cafés) are definitely worth visiting.