The Rainbow Nation of South Africa truly is a unique crowd. We have our braais, sunny skies, traditional greetings, and words that are understood only by other Saffers - no matter which of the 11 national languages they might speak.
It's only natural that you'd want to blend some of that delicious Mzansi-flava into your writing, and we encourage it wholeheartedly. (Un?)Surprisingly, the exact dialect with which you write your book can have repercussions. Have you noticed the ENG-US button at the bottom of Word (and in most other word processing software?) Most people just shrug, thinking "Ugh, what's the difference? English is English, right?"