If I am not wildly mistaken (altho, that's happened before) I believe this song title derives from Guantanamo Bay, in Cuba, which has or had a lovely beach before the US Navy sailed in. A woman from Guantanamo would be called a 'Guantanamera'.
And this song has absolutely nothing to do with the Chinese-Irish WWF wrestler, Wonton O'Meara. un hombre sincero, ChuckE