I'll caveat my comments by saying I've never been to Venice. However, I lived for three years in Sicily and have spent quite a bit of time in Catania, Palermo, Naples, Rome, and Florence.

If by "pubs" you mean a typical American/British/Irish type of place, I think you'll find them few and far between. Italian style "bars" - unless you visit hotel bars - are more of the family coffee/pastry shop type of places that also sell beer and wine. You may find the occasional Irish pub or a disco but the atmosphere of a pub crawl in Italy is going to be much different than that to which you are accustomed.

Enjoy your trip!