Mahabalipuram's restaurant strip runs along the beach road and the main bazaar. Most places serve the standard traveller menu of Indian, Chinese, and continental dishes. The local speciality is fresh seafood — the catch comes directly off the beach, and grilled fish or tiger prawn masala at any of the beachside restaurants is reliably good and very cheap by Western standards.
Moonrakers on the beach road is one of the older establishments and stays busy for a reason: reliable seafood, cold beer, and a relaxed roof terrace. Le Yogi nearby has a good-value thali and is popular with families. For South Indian breakfast — idli, dosa, vada — any of the small local restaurants off the main tourist drag will be better and cheaper than the beach places.