Where is the best place to rent a Villa for 2 weeks,
Are you serious? That is a huge area. Where do you want to go? It could be Naples, Sorrento, the Amalfi coast, Salerno and, of course, even further south the whole boot of Italy. There is no single, best place for a villa unless you can better define the area you are interested to see. You also need access. How are you getting there? Not trying to snarky but that is a very vague question. A little refinement would be a big benefit to all.
Your question is unanswerable as posed.
How would you answer the question: "What/where is the best place to stay south of San Francisco?"