The sad thing about the immediate surroundings is that the restaurants are actually shockingly-poor representations of what South Africa has to offer. We visited four restaurants located around the market and found service the service either to be extremely slow and unprofessional (even though the restaurants particularly weren't busy) or the food to be somewhat disappointing.
Perhaps we just picked the wrong restaurants, at the wrong time, but I can't imagine I'll ever be tempted to have lunch at a restaurant around Green Market Square again.