I have propagated tropical Hibiscus from cuttings. They're very easy if you know what to do. I usually take cuttings froma straight stem, about as thick as a pencil that had a previous bloom on it. about 8-12 " long but I've also propagated 4-6" cuttings from just anywhere on the plant.
You can get more info on propagating tropical Hibiscus at http://trop-hibiscus.com/rooting.html
I'm on the tropical hibiscus mailing list (thml) on yahoo groups. They give tons of valuable info on caring for, propagating, collecting seeds pods, fertilizing etc on Hibiscus. You might want to check out the American Hibiscus Society on the web.
They put out a wonderful book which I just bought.

You can also propagate them in water, in glass jars/cups/shot glasses (clear) in the windowsill.