Most people in SE Wisconsin, from what I've seen, say soda. I say soda, because saying pop sounds like you are 4 years old
I have never heard a drinking fountain called a "bubbler".
Geez, Sweetness, I lived in Milwaukee for 12 years and everybody used the term "bubbler". Funny how a short trip down the interstate makes such a big difference.
Other Milwaukee-isms were "up North", "hey" and "dere" as in "that's a nice coat you got dere hey", "where's the bubbler, hey?", etc.