I had problems with rotting on one of my cutting. It started out as a twelve inch cutting but after 3 or 4 failed rooting sessions all I had left was about 3 inch and one last chance. I had tried the bag, soil, and water bottle techniques all failed. So I went with the water rooting route and it worked. There should be a write up on it somewhere. This is what I would do if I were you.

I would start by cutting all the soft stuff off. Use a clean razor to do so. When you get to the hard, and healthy part cut it at a little bit of an angle so that it won't sit flat when it soaks in the water. Dip in rooting hormone, and let it dry for five days. Get a plastic cup not a clear one though. Roots don't like the light. Make a solution of super thrive and water. Soak it in the solution for about a week or so, no longer then 3 weeks. Change the solution out every couple of days. Till the bottom of it starts produces bumps, or what they call popcorn. Once it has popcorn put it in soil and cross you fingers. It should start rooting. Good luck.

My post on my three inch cutting.

http://forums.gardenweb.com/discussions/3232888/never-give-up

Oh, NO! After you mentioned "the soft stuff", I examined my cutting. It is hard at the bottom but very soft through the whole middle to almost the top (my second photo). It may be only two inches left if i cut it. I am so sad! how much of the cutting should be in the water with this method? an inch or more?

This is an update on my cutting. I wasn't brave enough to cut
anything off, just tested with a pin like others suggested and the sap
was white. So... I got a rooting hormone and a perlite/soil mix and
planted my cutting into a plastic bottle. it seems to be happy and you
could clearly see new leaves forming. I haven't seen any signs of roots
yet but I am excited it may survive! With the fall weather coming, any suggestions on when to bring it inside of the house?

Looking good! Looks like you saved it. Congrats!

Bring it in when nights get into upper 40s. Of course the warmer you keep it, the faster the rooting will be. You should still have some warm weather for a while in Nevada, right? What zone?

I don't know for sure, the Nevada interactive map says I am in zone 7A.

You're on the right track! Now just leave it alone in a warm area and forget it for at least a few more weeks. They like to be left alone when rooting :)

I am so excited about new leaves and growth but just came across some posts saying that plumerias must be kept dormant during the winter (?) I am not sure what to do now. I don't know for sure if my cutting has any roots (haven's seen any yet). Do I keep it active as long as possible? Do I need to keep it inside of a dark room and cut the leaves off?? Should I stop watering? There are so many threads on this forum, I am lost . Also, don't want to kill it :-(

the cutting will go dormant on it's own if it needs to. Some don't if they are kept warm. If you don't have roots, you shouldn't be watering anyway. I'd leave it alone, make sure it's warm and let it do what it needs to do.

so my cutting survived the winter without going completely dormant. It had three leaves left. Now I am seeing a new growth and new leaves are coming out. How do I know when to re-pot it and when to start to water/fertilize?

That's great. It is probably ready to place in a container right now. The best approach is to cut the plastic bottle vertically on the sides and open it like a clam shell to remove the root ball and gently place in a 1-2 gallon container with your fast drain soil mix of choice. If you look at the slight vertical wrinkles on the stem you can see that it is thirsty. Once its in the new container then water and lightly fertilize (no more than 1/2 recommended dosage) for right now. My preference would be a weak solution of water soluble fertilizer but you could probably use whatever is handy.