"Say you, say me, say it together, naturally". Davkett, I'd be more inclined to think that the man - it's a man who sings - wants the woman to practise saying "you and me " aloud, so she gets used to linking both words, that is both of them, "naturally". I agree with Goldmund, here...
I'm a big Lionel Richie fan and a native english speaker, and I'm pretty sure that it is say "you", say "me." As far as analyzing the song's lyrics, it is not a love song at all. It is a song about people getting along and even has a reference to Martin Luther King's "I have a dream" speach which is about all people of all races living together in peace.