I live in the area. As the previous post says, Alhambra is a must see place in Earth. If you have never been there, don't hesitate.
Concerning the Nazari Garden, I wouldn't advise you to go (have a look, some pictures here). It's a nice place, close to the port (no more than 20 minutes), but nothing special.
If you know which Winery is, I can tell you my opinion. Could it be a rhum factory? There is one in the port area.
Motril is not a touristic town, but it's quite close to Granada. If you don't want to take the excursion, you can always walk by yourself in town (again, not beautiful at all) and maybe have some tapas. The port is one mille and a half away from the town. There are public buses. Taxi should cost about 10€.
Anyway, should you need more information, let me know.