For some reason I've always had a fixation with the language aspect of Shadowrun but one thing I've always wanted to find and yet so far have failed to locate is a language distribution list or map for the Sixth World or at least North America.

For instance: In SoCal, most people speak English but a lot of us that live in the area have picked up some Spanish. Depending on the area, some Yiddish, some Mandarin, etc etc.

Is there anything like this that delineates the languages most commonly used in certain areas of Shadowrun?

i'm not aware of any maps, but the 3E Shadows of North America sourcebook had percentages for "major languages spoken" in the "at a glance" factblocks in the chapters for the different countries. However, because of the national scale, those stats aren't very detailed, e.g. the languages entry for the UCAS is "English 91%". IIRC it's also not defined what level of language proficiency the percentage is supposed to signify.

IIRC the Sixth World Almanac also lists major languages of the various countries but without any percentages.