Have just come back fm first visit to Cape Town.
A lot of this might be common knowledge but some may be useful (hope so).
i) Parking - multi storeys are of course ticket operated and there are several in the City, not overly expensive either and practical.
ii) Otherwise you will be using a parking marshal - either an official one (employed by the Council) with a badge and receipt machine or, especially in the evenings, an unofficial one - and they pop up everywhere. Tell the official one how long you think you're going to be, pay him/her and ask for a receipt. If you overstep on time simply pay more when you get back to the car. Unofficial ones you don't have to pay for but we got the impression that if we didn't, we might regret it. So we always gave them a few rand either on arrival or just before leaving. They will guide you in and out of your space with much hand waving and claim they will look after your car while you aren't there and they seem to have their own 'patches' too. We always paid a few rand and didn't have a problem so whilst you might have views on this unofficial payment system, it does seem to work and most were friendly and grateful for a small payment.
iii) Only park facing the direction in which traffic is flowing - don't cross over the road and park the wrong way round - you will be fined.
iv) watch out for mad Capetonians in fast cars who will happily overtake you on the left (keep your wits about you and use all mirrors) and very slow middle lane hoggers - both abound.
v) CT roads are excellent - fast access to city from suburbs along motorways and A roads and very clearly signed.
vi) When hiring a car think about where you are going to go. We hired a little Nissan Micra which had a very hard job getting 4 of us up the hill to the Table Mountain cable car. Camps Bay is also very hilly. If you go out to the Winelands, some of the mountain passes are VERY hilly (understatement). Much of the southern suburbs is undulating. If you opt for a small car and there are lots of you (or some or all of you are overweight) you will struggle and could damage the clutch, tyres or both. Be warned! Better to upgrade a notch or two on engine size.
Hope this all helps.