The U.S. embassy is in Pretoria; there's a consulate in Cape Town.
If you specifically need an ambulance, you can get one by calling the special ambulance number or through the general emergency number. If you intend to do scuba diving in South Africa, make sure you have DAN membership, which will be honored by Divers Alert Network South Africa (DANSA).
U.S. Consulate, Cape Town. 2 Reddam Ave., Westlake, Cape Town, Western Cape, 7945. 021/702–7300; 703/439–2301; southafrica.usembassy.gov. Mon.–Thurs. 8–5, Fri 8–12.
U.S. Embassy to South Africa. 877 Pretorius St., Pretoria, Gauteng, 0001. 012/431–4000.
DANSA. 0800/020–111; 27/828–106010; www.dansa.org.
General emergency. 10111; 112; 107.