I believe that making English the official language of California would be inappropriate because it would constitute an insult to Hispanic Californians.
It would indeed be ironic, and a slap at Spanish culture, if California were to discourage the use of the Spanish language. The state's very name and the names of its major cities, streets and mountain ranges are of Spanish origin. California is known for Spanish architecture and Mexican food.
Let us not forget that California was once part of Mexico, which was once part of Spain. Spanish-speaking people certainly have just as much right to live in California as anyone coming from Europe or the east coast.
Maybe it is we English-speaking Anglos who should learn Spanish, so that we can show proper respect for the people whose culture we have borrowed so much from.