Marinas place is fantastic. It's spotless, very functional, and is easy to find. I wouldn't worry about the location. Naples is all about character & texture. Truth is, your biggest danger is getting hit by a scooter. I will stay here again and again. I've stayed in dozens of places using AirBnB and thus far, Marina has been the most considerate and professional host.
Also, the best pizza in the world is pretty close.