That time of year it is not worth gambling a trip to the Western Cape, and no doubt flights for you to Jo'burg will be cheapest. There is a Facebook group called SA Climbers Liftclub (https://www.facebook.com/groups/saclimbersliftclub/
) which may be of use to you, and I agree that Boven should be your priority.
I will be looking for a climbing partner in Durban from 20 to 27 July. I am originally from Durban and know the various crags well, and basically I have some unfinished business to attend to up there, and although they lie above 25 you will have plenty to do. To repeat myself, try get to Boven!