Unfortunately, this commercial slogan encompasses about as much as most Americans profess to know about the Italian city of Naples; the truth is that the Neapolitan palate is actually a bit more developed. Pasta is eaten in endless profusion, while seafood like octopus has made its way into many traditional dishes.
The basis of Neapolitan cuisine is its use of local ingredients like tomatoes, basil, and a variety of cheeses; hence food staples like the ubiquitous pizza Margherita. Pizza joints are everywhere, although those with a little history and the scrutiny of amateur pizza critics the world over are mainly in Centro Storico, along Via dei Tribunali in particular. The famed Di Matteo and Pizzeria Sorbillo can be found here, while the exceptional L'Antica Pizzeria Da Michele is south on Via Cesare Sersale.
Head west to Vomero for the great selection of cafes and gastropubs found amidst a number of local businesses; Via Alessandro Scarlatti will be your main food artery. Between the Villa Comunale and the Castel dell'Ovo on the port to the south are a high concentration of pasta and seafood eateries, while west near the city's central station on Piazza Giuseppe Garibaldi are plenty of further options.
When in Naples, it's a given that you'll be eating pizza and pasta with high frequency, although you'll find snack options, Asian cuisine, and even a number of good bakeries/gelaterias if that's what you're up for. If you're at a loss and want authentic Italian, keep an eye out for trattorias; they're the equivalent of an Italian diner and will often prove to be a cheaper alternative.