Lots of people come to this site asking for suggestions and say they would like to visit places in Italy where they could enjoy wine, good food and commingle with locals.
What are we supposed to say?
Is there a corner in Italy where you cannot find wine? They make it even in the Alps where it's too high up to grow grapes! Likewise with food. Is there a region in Italy where food is nasty? I can't think of any. I'm glad at least you didn't ask where to find the locals.
Beaches. Italy has 8,000 km of coastline (5000 miles). I can't think of a coastal region that doesn't have some beautiful coastal spot. Maybe the coast of Veneto or the Romagna are not the top of my list. But the former has Venice and the latter the best nightlife. The best beaches, IMO, are in the islands, particularly Sardinia, but also all others, including the smaller ones. To the south of Rome, the Amalfi coast has some beautiful spots, beaches are small and pebbly there. The Cilento has great spots too. Calabria or Maratea in Basilicata are great, but far. Same with Apulia (Gargano, Tremiti islands, Salento coast), great but far.
Every seaside location will have nightlife in summer. But obviously the bigger the place the larger the crowd. Cities like Rome, Naples, Florence, etc. have plenty of nightlife too, even though not necessarily beach locations.