Hi Ben,
Taking into account the size of most SA's trout streams. I have a 9' 2wt Greys XF2 Streamflex, which is really a sweet rod fishing a dry fly, soft hackles and light nymphing smaller water at close range. In terms of versatility and having to choose a single weight rod considering early and late season a 3wt in my opinion can cover more options in terms of wind, also fishing streamers and still fishing dries and nymphs. So a 3 will probably be my first choice.