Living in Southern California I often encounter immigrants who are bilingual but feign ignorance of English went it suits them. There are also many locals who appear to be stereotypical English-only speakers who are also fluent in 1 or more foreign languages but rarely get the opportunity to use them. I refer to such folk as "slylingual".
A friend of mine is married to a very nice blonde "wasp" lady who also happens to be fluent in Spanish. One time the couple was dining at a family-owned Mexican restaurant. Two young men waiting tables were openly chatting in Spanish about her physical endowments and what they would like to be doing to her in the most explicit terms. At the end of the meal when she paid the bill she told the proprietress in perfect Spanish how offended she was by the men's graphic sexual comments. The owner, who had not heard the men's earlier conversation, was appalled by her sons behavior and apologized profusely. As the couple walked out the door they heard Mama "tearing her sons a new one".
Hadn't heard that term, and I live in AZ where many people speak, try to speak, or don't speak Spanish. So I looked it up in the Urban Dictionary. As you can see, their definition varies slightly from yours, but I think it's the same basic idea.
Closest thing that I've experienced was back in 1991 when I traveled south to Cabo for the "Great Eclipse." We flew in and out the same day, as the eclipse was near noon on a Thursday and we were only able to get that one day off work.
I speak very little Spanish, so I learned what few phrases I thought I might need ahead of time with the assistance of a Spanish teacher from my school. After the eclipse, we went to a local bar where we intended to order champaign to celebrate the event. So we sat at the bar, and when the bartender approached, I struggled in my "best" Spanish to first greet him, then order a bottle of champaign with two glasses.
He patiently waited as I recited, stopped, started over a few times, and finally finished my request. When I was done, the bartender, smiling, spoke in perfect English saying "So you and your wife would like to celebrate with a bottle of champaign?" Some of the other patrons, hearing the exchange, broke into laughter. I was only slightly embarrassed, but now, in retrospect, I think maybe I was being slylingualized for the enjoyment of the staff.
Martha (if you're reading this): This is my 821st post. I just passed your post count. What do I win? Wait ... I just realized if you do respond, we'll be tied again. Never mind. 