Regarding mapping quality:
For Poland, this mapping returns pl
(Polish), de-PL
, yi
(Yiddish) as in http://www.i18nguy.com/unicode/language-identifiers.html, which is certainly incorrect (should be pl
only).
Everyone in Poland speaks Polish unless he is an immigrant. There are some ethnical groups which have their local languages (notably Silesians speak Silesian โ szl
, Kashubs speak Kashubian โ csb
, neither of them included on that list!), but they are bi-lingual, and speak Polish fluently. Their languages are regional heritages and are difficult to understand for people living in other parts of Poland. Yiddish is a language of Jewish minority which is practically non-existent in today's Poland, and they also speak Polish. There is some German minority, but I believe they also speak Polish.
Polish is the only language universally understood in Poland. Furthermore, It's more likely that some randomly picked Pole will understand English, French or Russian rather than Yiddish, Silesian, or Kashubian. German is obviously somewhat known but as a foreign language. On streets, you can also hear Ukrainian due to their recent immigration. But they also understand Polish due to historical reasons and general language similarities.
Both CIA World Factbook and Infoplease are more accurate on this topic: