I used to think in Spanish. I used to tell stories about Mickey Mouse and magic and witches flying on brooms and pause only to ask my tia "como se dice dragons?" before continuing with my tale. Today I think in English and am fully aware of the thought-process in my brain as I work to translate what I want to say from English to Spanish as I’m speaking.
My father and his family came from Monterrey when he was 11 and he used to tell me how he had to repeat the sixth grade because the first time through he didn't understand English. My mother and my grandmother, on the other hand, were both born in the States, though my grandfather came from Guadalajara. Even though both of her parents spoke fluent Spanish, my mom grew up with only a love of singing along to norteño music as her own connection to Spanish. Still, she encouraged our bilingual upbringing—even when we grew to resist it as our worlds expanded with English-speaking friends and the knowledge that we didn't have to respond in Spanish.