How do you say can you speak English in California?

You say I speak Spanish. If you mean how do you say I speak Spanish in Spanish, you say Hablo español.

You could say "Eu só falo inglês." which means "I can only speak english."

je parle anglais

You say, "¿Podemos hablar inglés?

The imperative Speak English translates as:Sprich Englisch (informal)orSprechen Sie Englisch (formal)