Coastal town for a month or two?

With almost 7500Km of coastline is really very hard give suggestions.
In my region I can say that Rimini could be an option. Isn't a too big city, wide sandy beach (full of optional), touristy but for sure not overcrowded this year, a lot of fun and nightlife for any age, a beautiful historical center usually skipped by the beachy tourists (so in fact there is a "normal city" and a "seaside city"), a wide range of accommodation at 200/300m (or less) from the beach, good connection by train to move to inland Emilia-Romagna, Veneto and in general the Adriatic side of Italy. Around Rimini is even plenty of medieval villages and towns, where you can enjoy daily trips (by car, but even by bike or walking), knowing the culture, architecture, the food...

check with the locals. they probably have lots of good advice on places we don't even know about.

I'm thinking maybe Cefalu could be nice?

The beaches in Tuscany may be a good option. Slightly less touristed than Rimini or Cefalu, for example. Look at the Maremma.

Hi Jimena, does it have to be in IT? If so, I loved Cefalu. Expect to gain some weight because the cannolis don’t get any better than what you’ll eat there. In the late afternoon / early evenings, this is where the elderly men dress to walk the passeggiata.
If you’re open to places outside of IT, try the Algarve in PT. I really liked Salema.

Hi Mari! So far Cefalu looks like our favorite option - it would give us a base from where to explore Sicily as well. We are also looking into Puglia or somewhere around Bari - it will also depend a lot on the accommodation options of course! Portugal is another option. We traveled around Portugal for a month in 2017 and loved it, but focused in the route between Lisbon and Porto and then back driving right by the Spanish border, so we've yet to see the South. I'll check your recommendation out!

My favorite salt water waterfront places in Italy are Liguria:Santa Maria Ligure, Camogli, Portovenere, and Puglia: Polignano a Mare and Monopoli.
Fresh water: Bellagio, Lake Como and Ranco, Lake Maggiore.

Interesting differentiation tween the waters, Suki!
OP JL, if Cefalu, then you could have the chance to escape the crowds with daytrips inland to such places as Petralia Soprano. If Monopoli, there'd be daytrips to escape crowdage at places all along that coast (e.g. St. Vito) plus inland. *If food is a factor, note that Polignano is one of Italy's great gelato meccas.
I am done. the end.

A lot of these excellent suggestions are pretty small towns. You might look at Chiavari for a nice place that's a bit larger.

5000 miles of coastline to choose from. The list is endless.
Some options for each regione (in alphabetical order):
ABRUZZO: San Benedetto del Tronto
BASILICATA: Maratea
CALABRIA: Tropea
CAMPANIA: Sorrento or Positano or..(too many)
EMILIA-ROMAGNA: Cesenatico, Rimini, Riccione, Cervia.
FRIULI-VENEZIA GIULIA: Lignano Sabbiadoro
LAZIO: Sperlonga
LIGURIA: (Too many to choose from) Cinque Terre, Camogli, Lerici, Moneglia, Laigueglia, Santa Margherita.....
MARCHE: Senigallia.
PUGLIA: Vieste, Otranto, Polignano,... so many more.
SARDEGNA: Santa Teresa di Gallura, Alghero......
SICILIA: Mondello, Cefalù, Giardini Naxos, Castellammare, .....
TUSCANY: Versilia area (Forte dei Marmi to Viareggio), Castiglioncello, Castiglion della Pescaia, Porto Santo Stefano.
VENETO: Lido di Jesolo, Caorle, Cavallino

Hello Jimena
When travelling up the Adriatic we stayed in Polignano a Mare for 2 nights. Very high up but you can walk down to the shore (very rocky) we then travelled up the coast and stayed in Senigallia-(south of Rimini) lovely town with a historical area and miles of lovely beaches. It was an area I wish we had spent more time. The hotel we stayed at was just across from the beach and very reasonable.

Lerici-Tellaro area is nice. They are small, but you are so close to so much (Portovenere, La Spezia, towns along the train line within easy reach)
Will you have a car?
How about an island, like maybe something on Elba?

Thank you all for your advice! There are indeed SO MANY OPTIONS.

We're actually currently looking into Ischia! Seems like a nice island, rather cheap, from what I read not everyone speaks English so I'll get a chance to keep practicing my Italian... I'm pretty much sold!

Great idea--large enough to have plenty to enjoy, and close enough to plenty of great places--lucky you!

Actually, I wouldn't choose a small island for a month, much less two, because of the need to hop on a ferry for off-island day-trips. But I always have a long list of day-trips to take; I'm not one for spending time at a beach or taking long rural walks. I can see than an island base would be a good option if you want to relax and find that difficult to do if there are too many convenient options. Nonetheless, I recommend that you research the cost (in both time and money) of the off-island trips you'd want to take.

Hi acraven! We're not actually hoping to take lots of side-trips! We mostly want to stay put, practice the language, work from home, go on walks, etc. So being on a island is not a problem :)

Locals prefer Ischia over Capri which might be right up your alley.

I have heard wonderful things about Ischia and hope to go within a year or two. Looks like Ischia has many more sandy beaches than Capri.