Somewhere in this house I have a book on US Insect Pests and that caterpillar is on the cover. I can't find the book but I do remember not being impressed with the moth it made. I see them every year. By the time they are this big they are almost done growing and soon will climb down and pupate.

It seems to be Drexel's Datana. I don't know if that's good or bad.

Here is a link that might be useful: Drexel's Datana

nice thing about clusters on a bush is you can clip off the branch and dispose of all of them at once.