La Passeggiata - All year?

Keep in mind that it is not an organized event and if you were to inquire to a local, they probably would look at you funny, recognizing the term, but not as an event to watch or probably even take part in...just something you might do... like walk the dog. In larger cities with many tourists and non-locals, it may be less evident...there will be people all over all the time...but in a small town, as the tourists leave and things quite down, you will certainly notice the locals out and about, strolling, stopping to sit or talk to others, enjoying the last light of the day. So forget about Venice and Rome, except in the more remote parts of the city, certainly go for a stroll though. Even Sorrento may be more tourists than locals, though in October, you might have a fighting chance, Sienna might be your best bet.

In the cities you are visiting, especially in the main downtown streets, there will be people strolling 24/7. It slows down during meal time (1pm to 2pm at lunch and 7:30pm to 9pm at dinner), and of course it nearly stops during sleeping hours very late night to early morning. Venice strolling never stops in the main calles between San Marco and the Station. Siena has nearly constant strolling in via Banchi di sotto, Banchi di Sopra and via di Citta and Piazza del Campo. Rome never stops strolling anywhere in the Centro storico. It might slow down a bit at night.
Sorrento has constant passeggiata in or around piazza Tasso.

One of the best places in Rome for la passegiata is Piazza Navona in the evening way into the night (avoid vendors of tacky souvenirs). Any major piazza will do, almost anywhere in Italy. Of course, many of your fellow strollers will be tourists, while many Italians are at home with recreational electronic devices. By that I mean video games, tv, ipads...

I was in Verona in February, definitely off-season, and La Passeggiata was in full swing in the evening.

In Sorrento every evening, the shops are also open to 8-9pm. In addition, after church on Sundays during which Corso Italia is closed to traffic.

Of all the places we've been to in Italy, Sorrento had the most noticeable Passeggiata and it was wonderful. It was after sunset, from Piazza Tasso south along the main street. So fun to watch and be a part of. The Italians were all well dressed, strolling along, some eating gelato, and stopping all along the way to visit and talk to people they knew. We've been there many times from early June through August, haven't been there in Oct but my guess is if the weather's nice, they'll be out.

I agree on Sorrento's passeggiata - it's fantastic. I wish my city did it (weather kind of prohibits for part of the year). I was just in Sorrento, and they close the main road around 7:30pm and people start strolling. It occurred every night we were there. Great people watching, great way to slow down, relax and enjoy. We didn't really see this in Rome, but maybe we were not in the right place at the right time.

Best Passeggiate are not so obvious in the largest cities because there are thousands of tourists everywhere. So the entire historical centers of Florence, Rome or Venezia have people strolling. In any case this is where the locals would stroll on a Saturday or Sunday evening: FIRENZE (FLORENCE): via Calzaiuoli btw Duomo and Signoria. Also via Roma btw Piazza Repubblica and Ponte Vecchio. Since Mayor Renzi closed via Tornabuoni to the traffic last year, that is another spot. In summer also Piazzale Michelangelo. VENEZIA: Locals stay away from Venice as much as they can. But if someone is there strolling, they'd be anywhere along the main calli from San Marco to Stazione, in particular along the Strada Nuova. If they aren't tourists, they are likely locals who work in Venice and who are rushing to the Station or Pzza Roma to get back home in Mestre. ROMA: Via Condotti, via del Corso and anywhere around Piazza di Spagna. Also anywhere around Piazza Navona. VIAREGGIO: The summer passeggiata par excellence along the Lungomare. LUCCA: via fillungo and sorrounding streets SIENA: Banchi di Sopra, Banchi di Sotto, via di Citta'. AREZZO: Corso Italia (aka simply "Il Corso)
SORRENTO: P.zza Tasso to Corso Italia

Thanks so much to all who replied. The advise is greatly appreciated & will help make my first Italy trip special and memorable. I arrive in Venice Sunday at 9:00 -- can't wait!!!!!!!!!

In Sorrento - for a free sit down while watching the town go by, use the stone benches by the Cathedral on Corso Italia. Even better with a gelato bought from one of the nearby shops!