I've been thinking about Japan for some time. The girls, the history, the culture, the blowfish, it's got it all. Did I mention the girls?
Other than that, somewhere in Latin America would be good, but not Mexico at the moment, which is a pity, I love the food. Brazil loses points because they speak Portugese which would not be overly useful to learn; Cuba fascinates me, but her political landscape is probably a bit uncertain.
Guess I'll stick to Asia, which means Thailand or Japan for me.