A couple of years ago I watched a movie that had a scene that illustrated just this type of thing but via conversation. "
Lock, Stock and Two Smoking Barrels" had a great scene in which a bartender in East London was talking with one of the main characters and his slang was so hard to understand the movie had translation subtitles in the scene. The funny part was that the characters were actually reading the subtitles to understand the guy.
If we try too hard to create a full sense of local dialect readers may need subtitles to understand our writing.