Hmmmm ... how about a sign that says "I don't speak Spanish, I speak English!"
Let the official idiotarians find some way to twist that declarative statement into a civil rights issue.
I dare them.
The law is probably too vague to pass constitutional muster; the owner should welcome the order and then appeal to the state's high court for an opinion on the law.
The owner should have injected one word -- BETTER.
"For BETTER service, speak English."
It would be impossible, I believe, even for a knucklehead Civil Rights Commission, to argue that the service would be swimmingly the same to someone who does not speak a lick of English.
This is a 'better' way. It gets your point across but lets the "customers" know that they had better learn to speak English if they expect anyone to understand them here in the good ol' USA.