I've never spent summer in another country, so my possibly-biased opinion is that Cape Town is one of the best places in the world to spend a summer vacation.
Our niece and nephew (16 and 17 respectively) are visiting with us from Sydney for the next two weeks, so we'll be out and about doing the "tourist" thing and showing them the sights. One of the first stops on our agenda was Sinnful in Camps Bay - quite possibly the best ice-cream parlour in Cape Town.
I'm not sure that taking a walk down to Camps Bay beach, ice-cream in hand, was the best idea though. Our lovely smooth ice-creams quickly turned into crunchy delights as gusty wind sprinkled sand all over them, kind of like hundreds-and-thousands. Still tasted good though... :)