When to speak your native language

The 2003 film Shanghai Knights is a worthy sequel to Shanghai Noon. This even though the cleverly choreographed action sequences do start to feel a little routine, and it gradually gets very tiresome to see all the Forrest Gump-style manufactured prescience. But the nit I am picking here today concerns the matter of when characters speak their native language (and consequently there are subtitles on the screen).

When Roy (Owen Wilson) meets Chon Wang's sister Lin (Fann Wong) in a London prison, she and Wang (Jackie Chan) exchange a few words in Chinese, prompting Roy to practically command that they don't talk about him in their native tongue. Out of courtesy, they don't talk about him in Chinese any further, regardless of whether or not he is present.

Roy falls in love with Lin and asks Wang to put in a good word for him. Wang talks to Lin in private, and for no good reason, they talk about Roy in English, not Chinese! They might not know that Roy is eavesdropping (and it does seem somewhat improbable that he can hear anything clearly), but if they suspect it, would it not make sense for them to have this conversation in Chinese?

Also, how exactly is it that Lin and Wang learned English? For someone who hasn't been in an English-speaking country all that long, Lin seems to have a stronger command of the English language than her brother who has spent so much time in the American West.

Of course I do know the reason that that particular conversation is in English rather than Chinese: screenwriter's necessity. The screenwriters wanted a reason for Roy to get mad at Wang over something overheard, to parallel Wang getting mad at Roy over something overheard in the first movie. Dialogue like "Loy悪男LoyBaloney非常不誠実" might just not have quite the same impact on Roy's ego—in fact, that would have allowed him to hear what he wanted to hear, and in any case Lin does seem to like Roy back.

Lynette needs to learn a few things about 中国

The show: Desperate Housewives
The episode: "Everybody Says Don't," first aired on ABC this past Sunday.
What happened: Lynette's husband Tom (Doug Savant), while trying to convince his son to go to college, decides to go back to college himself in order to major in the Chinese language. Lynette (Felicity Huffman) thinks this is a silly idea and decides to sabotage Tom's college admission test by getting him drunk. After the test, Tom tells Lynette he thinks he bombed the Chinese test. Lynette suggests he buy a book, to which Tom says he can't learn Chinese from a book and explains that China is an emerging market and that he'd be more valuable to employers knowing Chinese. Lynette is surprised at all this, realizing that wanting to learn Chinese was not some kind of midlife crisis.
Why it doesn't make sense: So, Joey Murphy and John Pardee, you mean to tell me that Lynette, an executive in an advertising agency, didn't already know that China has a fast-growing economy? That she didn't know that in this age of globalization, American workers would be well-advised to learn Chinese?
Now, I have no trouble believing that Lynette would sabotage her husband. But I would think she'd choose her battles a little better. How about thwarting him from buying any more vehicles?