I would like to add too that there is nothing improper with a southern "accent" (and all its variants) . Improper English is improper whether its Bostonian or Hillbilly.

Y'all may sound coloqiual, but its sure a lot better than "you guys" which is the northern form of the plural and sounds ridiculous when used to address people in a group that arent even male.

Y'all can be used to one person if it implies plurality.

For example someone might say "Y'all coming to supper?" to one person if they mean them and their family.

Or if you go into a store and ask the clerk "Where do y'all keep the butter beans?" It implies the clerk and entire store staff- so that is plural.

This is why people are mistaken about the use of y'all or you all because when its used on one person it implies plurality.