I'm am employed full-time, and living with a friend in the Southern Suburbs. My individual monthly costs are as follows:

Rent: R2500
Electricity: R100
Phone and DSL line rental: R300 (shared with housemate, excluding calls)
ISP account: R125 (3GB of international bandwidth)
Food: R1000 (I don't eat meat, though, so this might be higher for someone who does)
Armed Response: R365 (shared with housemate)
Household Insurance: R72 (shared with housemate, this covers valuables up to R60000)
Hospital Plan: R691
Mandatory Bank Fees: R300 (+-)
Cellphone contract: R200
My recreational spending varies, but amounts to atleast R1000, and is usually higher during the summer months.
I don't have a vehicle since public transport is more affordable.

Total: R6653 (+-)

If you plan to come to Cape Town as a student or a worker, it's often best to stay with someone else. It really helps cut costs, which is necessary considering the petrol and electricity price increases coming into play.

If you're reading this site for just that purpose, do yourself a favour and have a look at http://capetown.gumtree.co.za/ - there are plenty of house- and flat-share adverts there!