Sighnaghi is a lovely little town that specialises in the manufacture of traditional carpets and wine growing. Two days should be sufficient to explore it. I recommend paying a visit to Bodbe Monastery, from where there are beautiful views out over the valley.
I spent two nights in a very friendly and hospitable family-run inn when I was here. If felt just like being at home! It was the middle of winter when I visited and there was hardly anybody around, so they gave me the best room, which had magnificent mountain views. Breakfasting and dining with the hosts proved to be a veritable feast for the taste buds, and I was free to enjoy as much of the house wine as I wanted.
Wine lovers will be pleased to know that it is possible to organise vineyard tours here, complete with tastings.