There seems to have been a GRAVE misunderstanding over the purpose of the petition. Being Italian myself, I understand what xdiesp meant, and I'll try to clear the point.
In AC1, the protagonist and the other characters he spoke to spoke American English. This was made to make the main dialogue understandable without subbing (and I second this choice).
Enemies and people in the cities however spoke their "original" language (Arabic for most, German and French for some templars/soldiers). This too is acceptable, since it helps the immersion of the player, even if it's not coherent with the whole "Animus translator" explanation (if the Animus translates languages understood by Altair in languages understood by Desmond, everything should have been translated to English).
In AC2 the language for the main dialogues will too be English, following the same principle of AC1. We do not want it to be Italian (it will be translated in the Italian localization anyway).
The problem lies with the other voices, those of the guards and other people: they should be in Italian as those in AC1 where in Arabic, but are not. They are in "fake italo-american" (as exemplified above, like Super Mario or the Sopranos). That is quite different from actual Italian, not even going near the difference between modern Italian and the language spoke in Venice back then (Italy has been united much later the year AC2 is set in, and at that time there were different languages for each different part of Italy). Since I suppose the Arabic in AC1 is modern, I can live perfectly with modern Italian in ancient Italy, as long as it least is Italian!
The fact that the AC2 dev team doesn't know much about Italian is also apparent from the name of the main character: "Ezio Auditore" doesn't sound at all as a realistic Italian name, not even as an ancient one. Maybe they found the last name (from Latin "auditor", listener) meaningful, but it sound pretty silly to an actual Italian.
Since they're even going to put in my birth city (San Gimignano), I'd be quite displeased if they made every passerby sound like some stereotyped mafioso from a 30's movie...