Safety situation in Cape Town

I would recommend spending the extra money for inside parking, just in the event of an opportunistic person trying to get your radio, or something in your car. 

Geez, when you say "inner" city it already sounds dangerous; but in all reality the Cape Town CBD has crime statistics on par with major international cities like London and Paris. That said, yes petty theft does occur, and though carjacking is not frequent - if you leave your purse in your car overnight it will be gone by daybreak. So if you do have the extra cash, finding a place with secure off-street parking is a huge benefit - almost more for the ease of finding parking than the safety aspect.

If you can't afford it, just make sure to leave your doors and windows locked and to leave your car EMPTY of all possessions. I've known robbers to break back windowns for a good looking belt. If you do this, you greatly approve you chances of avoiding violation.