Assuming they're using pure CSS for the font loading (which is standard for Google's CDN), yes, the browser will use a local copy in preference. (There's a way to disable that in CSS's font spec, although it's hard to think of a good use for that.)

Browsers try to load local fonts before remote fonts. At least anecdotally I've never seen a Google Font/Google CDN font bypass a local font, at least not with the default Google Fonts CSS code.

It does if the @font-face rule specifies a local() src.