Lingustic Terrorism

Darl and i had this really silly argument about speaking good English
You see, darl is quite a firm believer that one should speak intelligible English

It started with me relating a topic of discussion that went on during my grammar tutorial
some tute mateys in class were actually sharing the difficulties faced
teaching grammar to "neighbourhood school" kids who can't care less about
what's an adjective, verb, or noun etc.
the greatest challenge we face is enabling them to code-switch between acrolect (Std. English) and basilect (a variant of English, i.e. Singlish)
This, darl claims is a difficult task
and i don't know how the conversation went on from there
resulting in a final stand-off

The point is
Can one effectively code-switch when the occassion arises for the need to?
Is Singlish the bane of our society?
How can we maintain our "Singaporean-ess" and still remain intelligible to English speakers?