Sterkfontein Dam does not have much accomodation. I know of 1 or 2 resorts only on the dam.
Qwantani 058-623-0882 is an RCI timeshare resort, going there in December, but sometimes I know they let people in when the timeshare owners can't make it or when there's an opening. If no luck, ask them for the details of the resorts on the dam, they should be kind enough to tell you.
Awesome for bass and yellowfish, and other fish. You planning on going for bass only?