10+ Years Ago, on my first trip into SA (JNB) everyone (and I mean about a dozen ex-pats and SA folks) told me to SKIP the taxis (e.g. metered car taxi's not the minibuses). I've followed that advice ever since.
Minibuses . . . just don't. Don't ask.
Both hotels should be able to arrange a car to pick you up. 3544quebec's advice also works.
Tax Rates (Cape Town) -
http://www.taxiprices.com/taxi-fares...th-africa.html