Four Months in the South of Italy plus Sardinia - Bases Recommendation

The first thing that springs to mind is the Schengen limit on length of stay, which is 90 days for tourists. Do you qualify for any of the exceptions to that rule? If not, you would need to alter your plans- either shorten your stay, or plan to spend the remainder of your stay in a country outside the Schengen zone.

Thank for the note! We both have European passports so this is no problem.

Sorrento does not have to be expensive. We stayed at a B & B just off the main square, La Magnolia. We had a nice stay and a small breakfast was included. It's been about 4 years, the reviews continue to look good, but please, check other sources. Another place we considered was B & B Sorrento Queen. Went with La Magnolia because it was close to the train/bus station, I think about a third of a mile.

I wouldn't attempt to see Sicily with stays in just two places, though I agree that if you absolutely must do that, you've chosen the best two cities. Two weeks is the minimum I ever recommend for Sicily (that's with a car); I think four weeks would be fabulous. You definitely won't run out of stuff to do, but I think you really, really need more than two bases, especially since you'll be working during the week, which will severely limit your ability to take day trips then.

For Campania I, too, chose Naples and Salerno for a total of 11 nights last winter. I could have used more time in that area. I'd suggest investigating the Campania ArteCard, which could well pay off for you.

Lecce is quite different from a lot of the small Pugliese towns. It would be one of my bases for sure. Puglia is long and skinny, so I think more than two weeks would be called for there, and that's not even considering your desire to see Basilicata and Calabria as well.

It's a pity your dates include the main summer months of July and August when everywhere will be very busy and expensive. Also bear in mind the heat! August in particular is the big holiday month for italian tourists and everything gets booked up very early. If you could possibly arrive earlier in spring and leave max July you will enjoy it more, especially if you're supposed to be working too. To save money in July and August you'd need to go inland.
Sardinia: Alghero and Cagliari. Villasimius is tiny and totally touristy. Cagliari is a vibrant and pleasant city conveniently situated for visiting the south coast in both directions.
Sicily: Of the places you listed Siracusa and Trapani are my favourites. All the others are worth seeing but Palermo is noisy and chaotic, Cefalù more foreign tourists than elsewhere. Catania not as nice as the other two.
Puglia: Lecce and Trani are ideal. If you need somewhere cheaper on the sea, look at Vieste. A good place to stay and enjoy the coast and work but not good for touring around. https://slowtravelitalyspain.blogspot.com/2023/10/why-i-love-vieste.html
Unless you like both, don't underestimate the heat and the crowds in southern Italy in July and August!

Thank you everyone! This is very helpful.

@acraven, which other base for Sicily would you pick?

It depends on what places you want to see, but I'd like a location in the northeast -- probably Catania, Acireale or Taormina. I chose Catania (a working city with a nice historic center), but a Sicilian I met later recommended Acireale; Taormina is high-end touristy and expensive, with some folks really liking it and others (like me) being ready to leave after a couple of hours of walking past boutiques.

I'd also want a location in the west; I chose Trapani. I only saw Trapani (whose charms are not overwhelming) and Erice (very atmospheric) in the western part of the island, but others here have written about a number of things they enjoyed in that area. Whether Trapani would be more convenient than Palermo for visiting Selinunte and Segesta I do not know; I am not a big fan of Greek ruins.

I made a couple of trips into the interior from Catania (seeing the Villa Romana del Casale with its spectacular mosaics, Enna, Caltanisetta and Caltagirone) and would have liked to set up camp in a logistically-convenient town in that area for a few days. On large islands like Sicily, it's really nice to get away from the coast and into the less-touristy interior. A town in the interior might also work for a day trip to Agrigento, which is pretty far from both Siracusa and Palermo. I'm sure you could get to Agrigento from either of those cities with a rental car, and there are probably tours available; I'm not sure it would be a viable side trip via public transportation.

The above notwithstanding, I would want to be sure of adequate time to see the sights in Palermo and Siracusa and to visit the very nice Baroque towns outside Siracusa (Ragusa, Noto, Modica, Scicli, etc.).

Salerno and Naples are both good spots, Naples for the scavi spots and museums in/nearby (and Caserta!), and Salerno for the coast visits (ferries to Amalfi, Positano, and Capri) and Paestum. I'm partial to Salerno as I lived there, but I also like it because its not so hustle and bustle-y as Naples :)