Such signs and notices reflect the needs of the local minority which apart from standard Polish also feels like using another language. Sometimes it is a completely different like German or a dialect of Polish, e.g, Silesian dialect which was heavily influenced by German.
Let`s start with Silesian dialect which some people consider a separate language - Kaufland chain has introduced bilingual boards in two facilities in Silesia region:
Funny. Mustard is no longer musztarda but zymft.