This time of the year is probably the best time to travel the Cape province's inland countryside. Around time we'll often have cool, yet bright and sunny, windless days - whereas during summer our inland countryside is terribly hot and often windy.
The only problem with visiting Cape Town from abroad during winter is that the weather is so unpredictable - your visit could co-inside with superb weather like this, or with two weeks of rain, often accompanied by wind. Sorry about that. :)