Color me skeptical of this claim. I know many people here that are fully bilingual, but they are like my wife's Italian parents, and put the highest priority on children being proficient in English.
So it would depend a lot on the wording of the poll question.
1. "Don't Speak English at Home"
2. "Don't Always Speak English at Home."
To the 2nd question, I would answer Yes. I use a ein bisschen Deutsch, un poco de español, un po 'italiano