Actually, the United States does not have an official language. Everytime someone tries to make one (usually English), the legislature strikes it down and calls it a states' right issue. In New Mexico for example, English and Spanish are both official.
Then what the heck was my high school US history teacher talking about when she taught us that English was voted over German as the national language?
While you are correct in stating that the US does not have an official language, this still does not give any credence to the use of multi-lingual ballots. The simple facts described below do however, negate the need for multi-lingual ballots:
1.By the time you reach voting age, those born in the United States speak english.
2.Per our immigration laws, you must be fluent in english in order to become an American citizen.
3.You must be an American citizen in order to participate in elections.
Therefore, anyone allowed to vote should be proficient in english.