I think comedian Billy Cyrstal would disagree with Singer's assessment of Yiddish. He told an NPR reporter a few years ago that Yiddish is a cross between German and Phlegm.

PS welcome Joe

I grew up in a neighborhood with many yiddish speakers, and could understand the gist of spoken yiddish --age 18 or so, i went to a play at 92nd st Y(MHA)and understood enough to get the jokes--but there are fewer and fewer yiddish speakers, (and i have less contact with those that do speak yiddish)

NY(C) english is filled with yiddish expressions--we schelp things (in tote bags perhaps), we nosh (on knishes) , we kibbitz, and even a irish man (conan o'brien) is a mensch--(when he is not a fool!)

we know the difference between a schmer, and smear, when we ess a bagel..(there is a ny bagel store, Ess a Bagel (yiddish for eat a bagel)--and we know what's kosher!

and while movies and television have made some of these words know in most american english, they still remain common only in areas with current/former yiddish speaking populations.