The thirty seconds it takes to read this will save you untold embarrassment and possible physical harm in the deep south of the US.
Y'all, a contraction for "you all," is second-person plural. Like ustedes in Spanish or vous in French.
I thought you should know.
And the one thing everyone agrees on is that Southerners, who actually use the word, are the ones who are most likely to insist it’s plural only.