Huffington Post has a gallery of what they call "fake teabagger signs," where I found the one above. He was trying to cite a common meme from a Maury Povitch show, but misplaced his apostrophe. "Y'all" is an abbreviation for "you all," but he seems to have confused it with "you'll" and "they'll."
Academics argue whether the "you" in "y'all" is implicitly plural. Some say it is, but when I lived in Texas (and to a lesser extent in Kentucky), "y'all" was often used when addressing a single person. When addressing a group and intending to address all of them, the term would be modified to "all y'all."