Hey, i suggest u to go on Wind, they have a data plan for only 12 euros at month u got like 10 GB of free web, after u reach 10 GB of web the connection speed goes slow, but u can still surf the web for free, anyway the option is called Mega Unlimited. The coverage with Wind is very good, u got 3G everywhere u go, anyway if u can try to visit the web site
Wind - Telefonia mobile, offerte internet mobile, tariffe smartphone and go the section Internet n look for Mega Unlimited, the cost of the option is 12 euros. Wish that can help u, have u a great trip here in italy, cheers.