I'm thinking of skipping top of South Island

The hot pools in Franz Josef are manmade. The only natural hot springs pools I'm aware of on the SI are in Hanmer Springs and Maruia Springs. Omarama also has some sort of manmade hot pools.

I've only been to the ones at Hanmer Springs, which is about 90 minutes drive from Christchurch give or take. The thermal pools are the main attraction at Hanmer Springs.

You should be fine winging it in November. Are you renting a car or taking a bus?

Not sure yet was thinking of bussing it .... Do u recommend car?

I do, but only if you're comfortable with driving on the left.

Sounds like a pretty erratic itinerary to me. Queenstown is way south and Abel Tasman is at the top of the Sth Island. Best to fly between the two and why would you double back to Queenstown? No reason to go to Blenheim, there are plenty of good wineries just outside of Queenstown as that's about the only reason to go to Blenheim. Nelson is a more attractive place to visit. I think you need to do more research yourself and then choose what you want to do, no one else can decide if something is right for you. Look up Naked Bus as they have some very reasoable prices and fits in your age group so you are likely to meet like minded travellers on those.

Here are some other bus links for you:

http://travelheadfirst.com/bottom-bus/passes-prices.html

http://www.intercity.co.nz/

http://travelpass.intercity.co.nz/itineraries/south

In addition to Air New Zealand, domestic flights within NZ are also offered by Jet Star airways:
http://www.jetstar.com/nz/en/home

In case you are not already familiar with them, these are two sites where travelers post reviews and recommendations:
http://www.rankers.co.nz/
http://www.rankers.co.nz/tags/bus-and-coach

http://www.tripadvisor.com/Tourism-g255104-New_Zealand-Vacations.html

If you want to drive around alone and enjoy the freedom of being spontaneous, stop wherever for as long as you want, then rent a car. If you would like to meet other young travelers with whom you can share your experiences, and also don't want to be bothered with driving on roads you are not familiar with, then take public transit. Or take public transit and rent a car when more convenient or desirable (say, to go someplace not covered by public transit). See:
http://www.nzta.govt.nz/resources/whats-diff-driving-nz/whats-diff-driving-nz.html

I would add to the above article that many of the roads on the South Island are winding. You can also get stuck behind slow-moving motorhomes, who should pull over but sometimes don't or can't. Fortunately, there are regular passing lanes on most roads.

I am in my 50s now and generally travel with my husband, but throughout my 20s I often traveled solo on public transit in foreign lands, and always made new friends of my own age, who I ended up hanging out with and doing things with. I had a great time, met so many people of different nationalities, and learned a lot. I ended up doing activities with other people that I wouldn't have done if I was on my own. (At 28, I am sure you will be savvy enough to be both open yet still a bit cautious with strangers when traveling through NZ, as you would be when at home in LA.)

My impression is that NZ is an extremely easy country to see as a solo traveler. It is relatively safe (as compared to most other countries), has lots of services and conveniences for tourists, its people are friendly and helpful, and English is the dominant language.

Magic Bus:
http://www.magicbus.co.nz/travel-passes/transport-only/