I dig post-apocalyptic stories written in dialect, because language evolves. It makes sense that over a long period of time—and cataclysmic events that separate populations from each other—that language would be changed a whole lot more than by the introduction of a few new slang terms.
Anyway, what I'm saying is this: post-apocalyptic dialect, BRING IT ON.
After the Snow, by S. D. Crockett: Willo drops the 's's off of his verbs and has spent so much time on his own in the wilderness that he tends to look at the world in animal terms, rather than people terms... which ends up being both a strength and a weakness when he goes out looking for his missing family.
Blood Red Road, by Moira Young: Saba doesn't use quotation marks and actually sounds quite a bit like a cowboy. I love her, her voice, her world (though I wouldn't want to live in it, what with the kidnappers and cage fighting and giant worms and whatnot), and this book.
The Reapers are the Angels, by Alden Bell: No quotation marks, no apostrophes, lots of beauty-in-the-midst-of-tragedy, Temple's grasp of the English language seems like she learned it via a decades-long game of Telephone. My favorite zombie book in recent memory.