Yes, Q. Folks in New Orleans are usually puzzled by the plural. I've usually sung "by the banks of the Ponchartrain" myself. Also, you're exactly right about Creole: many whites who use the term think it is improperly, and only recently, applied to blacks. But outside New Orleans, in Southwest LA, it has referred to black folks for a long time, so there are regional as well as temporal aspects to whom the word would properly refer to.