The power adapter that comes with your MBP (and
most cell phone and camera battery chargers - check the small text on the charger itself) can accept input voltages from 100-240V and 50 or 60 Hz. South Africa is 230 V AC, so for those items all you will need is a plug adapter to fit your plug into those outlets - available from Radio Shack, or any mall-type travel store. Note that
Apple's World Travel Adapter Kit may not include a 'type M' adapter, which is used in Mozambique, South Africa, and Swaziland (and has been mostly phased out in Hong Kong; Hong Kong is listed as a supported country in the Apple description, so if you are going to go that route you may want to call Apple to check).
For things that plug directly into the wall
without a power brick/adapter of some sort, you would need a step-down transformer - again, visit the travel store for that.
As for unreliable power, there's not much you can do if it just goes out (which happened occasionally to me in East Africa). In terms of "dirty" power, the AC-to-DC conversion carried out by the power brick filters that pretty well. You can buy a surge suppressor ('power strip') once you get there, or bring one.
Happy travels!