It's certainly informal, to many degrees unacceptably so, but only when one employs a strictly puritanical perspective. It is also quite conversational, because using proper words in normal conversation, while always understood by County denizens, can never be quite descriptive enough.
Take, for instance, the innocuous phrase, "Good Heavens. It is very cold outside this evening." A County resident might say, "Sweet bald-headed Jesus. Is it ever some friggin' cold out tonight." Same statement, but somehow, we've added feeling. Colloquialisms are the monosodium glutamate of the English language, and like any exotic and spicy food, at first they seem as strange as the locals themselves. But to carry the metaphor further, we can also understand that learning local cuisine helps one better appreciate local culture.