Yes, Orac, "O Sole Mio" is Neapolitan (i.e., in the dialect of Naples), which is substantially different from, say, Italian as spoken in Rome or Milan. It may be as different from standard Italian as the French in Quebec is from Parisian French or even as Yiddish is from German. I can understand some of the lyrics, since I speak/understand a little bit of Italian, but there are words and phrases I can't even translate without asking someone from southern Italy, since the dialect is so different.

Still, Spanish versions do seem to exist, and that's what Marion is looking for.