I think it would depend on the meaning of the word. Does the slang have a hateful or derogatory meaning, or is it a slur? If so, then no. If it has no hateful or derogatory connotations, then there's nothing wrong with it.
Technnically speaking the word 'OK' is slang and nobody gets upset about that.
Yes, in an informal letter it is OK to use slang.
No. It is slang and should not be used in formal English
no its an acronym the slang of ok is k or kk
OK is a slang word, and cowboys used it.
Slang-similar to ok
It means "ok" It is a slang-y way to say "all right."
All right IS American slang - you might also say "OK."
you so fly
Writers use slang because real people use it.
It's more a case of no one saying that they weren'tallowed.
You use slang in casual conversation, especially with friends.
Toddlers don't use slang. They use definate, literal words.