[Effendi]

Wind has a cheaper offer called "wap-pass" (don't be mislead by the name, it works with norma web APN too) at 3 euros but you have just 10 MB per month, which can be too little for your use. There's also Mega300 which offers 100MB/month for 8 euros.
If you need more data go with 3, the Naviga3 should pass from 50MB/day to 100MB/day in July (if I'm not wrong) still for 9€/month so it's really a good deal.
I have no experience with foreigners buying a prepaid card on 3, but I think it shouldn't be a problem using the codice fiscale, of course, and your passport. Activating the option is very easy, but I don't know if 3 has voice-promts in English so maybe it's better if you ask the dealer to help you with that.