I think even though I was born in Mexico and lived there for a while, I would likely now consider Spanish my second language based on how now my English is much more adequate (at age 7 my Spanish was at the same level as any other Native speaker but it has deteriorated over time due to being out of practice). The time that I have lived in the States, I have lived in mostly wealthier, middle class Asian and White neighborhoods (prevents me from finding many other Latinos, the ones I do find usually are like 2nd gen who don't speak Spanish well enough for a decent convo). Usually, I speak in only Spanish in Mexico (unless it's my siblings, we probably have not spoken in Spanish in like a decade with one another) mostly due to relatives just simply not speaking English well enough or it would be out of place to speak in English (it's also good practice for me). In the US I tend to speak in Spanish in private with my parents (sometimes in English depending on what lang. the conversation started in). If I am in public I only speak in English (I guess its a subconscious thing, my parents almost never speak Spanish in public anymore). The determining factor for me whether I speak in Spanish or in English with someone is their proficiency in English. Usually, however, if I end up discussing with a relative in English, it's mostly so they can practice with a native-speaking American rather than in some class.