None of these uses is "slang", which is language (typically words and phrases rather than syntactical constructions) currently fashionable among a relatively small speech community (typically young people).

1. We entertainers *for "We are entertainers" is dialect, African-American Vernacular*. 

2. You mad *for "Are you mad" is a sort of ellipsis called 'conversational deletion', described [here](http://english.stackexchange.com/a/66994/24489), and is common in all varieties of spoken English*.  

3. Don't ... ? *for "Doesn't ..." is non-standard but very common in the language of those who are indifferent to standard usage.

2, *conversational deletion*, is acceptable in informal conversation; the link describes its construction. But I urge you not to emulate 1 or 3: 1 will be taken either as mockery or an illegitimate claim to membership of the African-American speech community, and 3 is generally regarded as a mark of uneducated speech.