There are mixed opinions on whether edible or not. Mostly I’ve seen you can eat them if you cook the beans well - here’s another take on it:
“Practically all parts of the plant are edible, although the seeds are slightly toxic and need to be cooked well in two washes of water before they should be considered edible.”
http://www.easybloom.com/plantlibrary/plant/ornamental-hyacinth-bean-vine-1
Interesting. Some people of Mediterranean decent have to be careful with Fava Beans and must follow the same regimen when cooking them...