One of my friends is fluent in both Mandarin and English. When she lived in Taiwan, she paid a visit to a nightclub whose gimmick was that you had to speak English. The target audience was not foreigners but rather native Taiwanese who learned English as a second language. My friend didn't have any problems with this rule, but many of the guests appeared to be struggling to conform.
My friend paid a visit to the ladies' room, and there she overheard a conversation between two other guests. (They were speaking in Mandarin. Apparently, the rules aren't enforced in the bathroom.)
"There's this cute guy out on the dance floor, but I don't know what to say to him. My English is not very good."
My friend told her, "That's okay. His English isn't very good either."