There are restaurants all around the Piazza Navona, some less good than others. Check out the menus that are posted and see if it feels like a place you would enjoy....there is a mixture of restsaurants with different atmosphere. We enjoyed I Quattro Fiumi, great staff, very friendly, good food at reasonable prices. Of course, sitting there in the afternoon, with the beauty of the fountains splashing is a wonderful experience wherever you eat.