My father-in-law, a respected Rosh yeshiva, told me straight out that Yiddish has no kedushah to it, and it’s a big mistake to think it does.
I don’t have anything against people knowing Yiddish. However, I disagree with Joseph, who posted earlier that he respects those who speak Yiddish as a first language at home. I don’t like the fact that Mexicans only speak Spanish, and don’t speak English. Why should Chassidim be different? I’ve met Chassidim who don’t speak English, or only speak very little English. English should be your first language if you live in the US. You want to preserve your Yiddish? Go ahead, but not at the expense of English.