South African SIM card
European SIM card
USA SIM card
Whether you are using your regular phone or a travel phone, make sure to add the phone numbers and address of the places (hotels, restaurants, friends, business associates, airlines) and people you plan on visiting to your contacts or address book.
This will make calling and using maps easier (no need to look up numbers or google for contact details while you are traveling).
If you are planning on calling outside of the USA, make sure those numbers have the country code as part of their phone number.