Which language is the sexiest?
I personally think all accents can be sexy and be horrifically irritating. It is a combination of 3 things:
1) The tone of voice matching the accent.
2) The tempo of talk making the accent audible but not so slow that it feels like one is talking too slow.
3) The voice not remaining monotone (Italians and Russians are both well known for automatically avoiding this)
If these 3 things go well, you are pulling off an accent. If they don't go well, the accent you are trying to pull off will end up sounding annoying no matter how many hotties use it.
Who cares about the rumba? It's not sexy.
Spanish is spoken too rapid fire and staccato to be considered sexy. I often find it annoying.
French and Italian are both far sexier. Hell, so is English with a British accent.
I have a female coworker who speaks Afrikaans. She also makes that sound sexy. It's like a cross between French and German.
The least sexy languages are the gook dialects like Chinese and Vietnamese. Arabic is pretty bad too on the sexy meter.