This is definitely some sort of novelty/recreation. A quick Google search shows that is clearly NOT Al Capone's signature. As for a modern translation, this is my best guess:

When we say pay your tab, it's time to pay. No weed, no cocaine(?).
Leave your gun with the doorman.
Dispose of your alcohol if the police arrive.
Don't discuss politics, religion, crime.
Keep it civil. No fighting.
Drunks will be cut off and kicked out.
Con artists don't pull any schemes.
Don't mess with a woman who is taken.
No alcohol outside the premises.

Anyway, it's an interesting poster, definitely fake though. In the words of Rick Harrison, thanks for bringing it in, but it's just not for me.