Nicoise cooking is its own tradition, closer to Italian than to classic French cuisine. The old town is the best place to eat cheaply and well -- look for socca (chickpea-flour pancakes cooked on huge copper plates), pissaladiere (onion pizza with anchovies and olives), and salade nicoise made the proper way, without cooked vegetables. The Cours Saleya market is lined with restaurants, though you will pay a premium for the setting. For better value, wander a block or two into the side streets.