I think the multi-lingual ballots are printed for the bond issues, and state/local law changes, not the elections. Some of the propositions and law changes are detailed and contain a lot of information. Those are always included after the election choices. You probably couldn’t understand those in Spanish.
Personally, I believe that if you want to vote in the election you should be able to read English, but I think the fear is that some that do not fully understand the language will vote in the election, and then choose randomly on the things they do not understand. I don’t know for sure, but that is what I have heard.
It is fairly easy to pick up the basics of a language, but it takes a long time to become fluent enough to converse. As a paramedic, I come into contact with many immigrants, legal and illegal. almost all of them can speak minimal English. Very few can speak enough to get their point across clearly, and also understand mine. English is a very tough language to learn, much more difficult than Spanish.