Joke:

What do you call someone who speaks three languages? A Trilingual.

What do you call someone who speaks two languages? A Bilingual.

What do you call someone who speaks one language? An American.

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The truth is that many people tend NOT to take the trouble to learn the language of the countries that they are visiting, although once on the ground (meaning when they are in the foregin country), they may be inspired to learn the basics. So I don't think your Spanish-looking friends are conducting an experiment :)

"Good Morning" rather than Evening because "Good Morning" is used much more frequently than Afternoon/Evening. "Good Morning" is commonly used as an social ice-breaker or friendly greeting. Good Afternoon/Evening is mostly only used in formal situations, like when you want/need to make a good impression on a customer/boss/associate. Good Night is usually synonymous with Good Bye, and it usually means the speaker is signalling they are ready to call it a day (i.e. leave).

I didn't, but many Chinese still corrected my pronounciation anyway. :)

@ HI Darren,  I'm Chinese also.  You mistook me as a foreigner. 

@ yingguoning  因为阿拉老少看到企鹅，所以伐大用上海话讲企鹅。 我会说企鹅，但是不知道说的对不对。。。

我没有在路上问过人语言问题，但最近去便利店买东西顺便问收银台阿姨用上海话怎么说企鹅，她竟不知道，还叫出一个同事问了问，同事也不知道。看来上海人不怎么谈到企鹅。

hello，i am a Chinese，living in shanghai，i wish to enhance my oral English。I hope to make friends with you，maybe we can study each other。I can teach you Chinese（mandarin）