First rule of bank robbing is to make a note that is clearly legible and grammatically correct. When the teller can't read the note and is required to ask what exactly you need, then abort the mission and cut your losses.
A man in Washington D.C. did exactly that when he slipped the teller a note that she was unable to read. According to the Washington Post article:
Authorities say that most bank robbers use notes, not guns, but the wording must be clear to be understood. Court documents say the note handed over at the SunTrust simply read, “100s 50s 20s 10s.”
“The teller was confused,” the FBI agent wrote in the affidavit, noting that the teller understood the man to say “money” but nothing else. She handed the note back, and the FBI says he wrote, “all mona.” The teller sent him away. It was only after he left, authorities said, that a customer who was in earshot told her that the man was trying to rob the bank.
Convinced it wasn't him but her, the robber attempted to rob another bank three blocks away. Unfortunately, he wouldn't get the chance to take all the mona. Police aprehended the suspect immediately.
Sadly, he probably could have written the note in spanish and the teller would have understood it.