Hi Mr. C Welcome to the forum!

I have rooted many allamanda vines from cuttings. I usually take my cutting below where the plant has had flowers or new growth. I use powdered rooting hormone on the cut end and I stick it in a vase of water. Usually within 2-3 weeks there are roots on it. Usually I wait till the roots are about an inch long before I put it in soil. They seem to root easily it just takes some patience.

Hope this helps...and Happy Gardening !

Karen