I think that jews' ability to speak English with less accent is a minor factor, but not one of the primary factors. Certainly, they have a good ability to blend in with White Caucasian populations. White Caucasians are also unsuspecting of them and usually cannot detect a jew merely by appearance, whereas you and I have a better jewdar detector.
That's all. Jews talk like whites and light-skin spics still talk like spics (Aside from Fuentes who talks like a faggot Californian).