Folks
www.sars.gov.za/AllDocs/OpsDocs/Policies/SC-PA-01-06%20-%20Excess%20Currency%20-%20External%20Policy.pdf
Taking out of SA - unlimited if from an authorized dealer (your bank) but if a special dispensation and over the standard limit, may be worth declaring
Into other countries - depends on local regulations, many require declaration above a certain amount and you may be asked to prove the source
Back into SA, in theory everything should be declared. In practice - only funds in excess of what you took out (excluding the $100 you drew at the ATM somewhere)