1) Mock Spanish is not Spanish
2) Not all Latinxs speak Spanish
3) Not all Latinxs who speak Spanish want to use Spanish with white people
4) Don’t expect Latinxs to be your Spanish teacher
5) Being bilingual doesn’t automatically make you an ally to the Latinx community
These are all critical and important dimensions of which White native English speaking Spanish speakers ought to be aware, but I am not sure they help me decide when specifically it is appropriate for me, a white English-Spanish bilingual (who speaks more than mock Spanish), to speak Spanish to Latinxs in the US. I don't pretend to know the answer here, but with critical humility, I offer a second set of guidelines, that are undergirded by Dr. Flores' 5 above. I try to mindful of these when I consider whether to speak Spanish to Latinxs in the US:
1) If I am spoken to in Spanish by a Latinx in the US, who I do not know, I will converge to Spanish, or feel free to do so. Otherwise, I typically use English as a default. There are some contextual exceptions, but this is the general rule.
2) If, in that default, it is clear that my Latinx interlocutor is emergent in their English proficiency, then I will often say something in Spanish as an overture to bilingualism. The nonverbal and verbal responses here tell everything about whether the person would rather switch to Spanish or remain in English. Or it sets up the possibility to translanguage as the conversation continues;
3) If I have a close friend or colleague with whom I have developed a dynamic linguistic relationship, I feel free to speak in English, Spanish, or translanguage as the situation/topic warrants;
English is the language of centralized and institutionalized power here in the US. We leverage it in schools, employment, civic engagement. Spanish and other languages are deliberately and conspicuously minoritized (see this recent reaction to bilingual communication in Arizona), which can make it easy for the do-gooder White bilingual to think that just because they speak Spanish they should because it legitimizes bilingualism, and/or elevates Spanish. Dr. Flores, particularly in his disdain of Tim Kaine's obsequious use of Spanish on the campaign trail, makes the important point that it is not this simple, and that White, native English speaking Spanish-speakers have a responsibility that goes beyond embracing the "celebrate diversity" model of bilingualism.
Recently at a block party on my street, I was talking with a Latinx neighbor and his spouse, both of whom I knew to be fluent Spanish speakers, but with whom I had only ever spoken English (per #1 above). However, my neighbor's Venezuelan mother was visiting and attending the event. She spoke very little English. My friend introduced me to her in English (he didn't know I spoke Spanish), and she said hi to me. I asked her how long she was visiting for, in English, and was met with silence. I repeated, "Cuánto tiempo estará Ud. visitando?", o algo asi. This began a 30-minute conversation, in Spanish, that allowed us to learn more about one another, and for me to learn more about my neighbor (#2 above). That conversation that would have been impossible in English. My friend and his wife also learned that day that I speak Spanish. Now, with them, the default language is still English, but a translanguaging precedent was set (#3 above), which gave me some important insights about when it is appropriate to speak Spanish with Latinxs in the US. Thanks to Nelson Flores!