Alright, I've cut my plumeria. I have a 7" cutting that looks decent:
I don't know if that darker ring inside is normal or not, but I sprayed it with fungicide and have it wrapped loosely in a paper towel on a shelf. I have some rooting powder and perlite, so when I get back in to town in 2 weeks I'll mix up some perlite and soil and try to get it to root.
I also cut the main trunk down pretty far -- it's back in the garage now too:
We'll see what happens. The other plumeria has black tip, I think. I've sprayed it with fungicide and will continue to monitor it. Thanks for all the advice.