My last visit was built around visiting Milford Sound - you know the one pictured in beautiful sunshine and flat water to make that perfect postcard. It poured and was so foggy you couldn't see both sides of the sound at the same time! I was told by the locals that rainy weather is the norm. Don't get me wrong. The south island is the most photogenic place in the world. Just be prepared for four seasons - every day. No matter how you plan, the weather is unpredictable but that adds to the interest in your pictures. Just alot a few days whereever you go and enjoy.
I visited the New Zealand about 20 years ago for a November. I had planned on splitting my time between the North and South Islands. Started in the south and spend all but 4 days there. Just couldn't bring myself to leave.
The weather was good but variable. No real rain but fog and drizzle. The people were as friendly as could be except for Invercargle. The penguins near there were fun though.
I hiked for 4 days in Milford and it was beautiful. I tried to tip the guide but instead of cash, he really wanted my Pategonia fleece shirt. So I literally gave him the shirt off my back.
Mostly just drove around. The scenery was varied and all just beautiful. For shear beauty, only Alaska is a rival. Lots of farms, sheep and mountains.
I do recall I thought the food was so-so at best. Something called "pasties" - little meat pies. Dreadful. And fish bait or white bait, or something like, were considered a treat but weren't. Thanksgiving, I stayed in a fishing lodge and the owner prepared a feast for the 10ish Americans there. She really didn't know anything about US Thanksgiving and couldn't find a turkey, so it was roast chicken and just plain wonderful. Trout fishing and dinners were great too.
I spent two nights at an inn near Christchurch built from a converted horse stable. The owner treated me like I were a king of something.
I seem to recall that most things were relatively cheap. Except transportation (anything associated with oil). And clothes. I priced a pair of Levi's and they were $85, a bit pricey.