We wouldn't recommend it. Cape Town's only semi-reliable public transit is the MyCiti bus that runs from downtown along the Atlantic Seaboard past Green Point, Sea Point, Clifton, Camps Bay, and on to Hout Bay. We use it from time to time, but it's a bit of a hassle to sign up to and slow to use so we recommend sticking to Uber unless you're staying in Cape Town for an extended period of time.