I'm down here in good ole TEXAS where we all say Coke. I can't remember the last time I heard anyone in TX say soda or pop. I honestly think you would get a funny look in most parts of Texas if you asked for that.
My mom's whole family lives in Cleveland, and they all say Pop. I laugh at them every time they say it. But, I guess it's ok, cause they look at me like I'm nuts when I say "Ya'll". hehe