My husband and I will be traveling to Sorrento from Rome. We want to stop in Pompeii for the afternoon. Are the luggage storage situations secure? I understand there is a locker at train station and a storage at the entrance to Pompeii.
Any feedback would be appreciated.
I can't give a definitive answer because I don't have personal experience, but over the years of watching the discussions here about Pompeii I don't remember seeing any complaints about the storage there.
As with luggage storage anywhere, do be smart about what you leave in your bags, esp. no passports, no credit cards. Why take a chance? Keep them on you in a secured location, preferably a money belt or neck wallet.
I stored my bag at the entrance to Pompeii last year and had no problems. There is also a bag check in the Popmpeii train station (downstairs, near the restrooms, €3 per bag - Italy no longer has lockers in any of it's train stations since 911), but since the bag check is free at the site entrance, I'd leave it there (just a short walk from the Circumvesuviana station).
We didn't use the storage, but no one has reported a problem in the last six months here. And it comes up all the time.
If you are staying in Sorrento more than one night, you can consider visiting Pompeii from there. The Circumvesuviana train is very cheap, if often overcrowded. An all-day train ticket is only about 3.40 Euros, so you could go somewhere else (but not Positano - no train) the same day for "free".