I've always heard about Andy Milligan movies, but have never had the good fortune to see one. I have heard they are awful. I HAVE seen "Monster A-Go-Go" on MST3K. I can't conceive of anything being worse, and I HAVE seen "Manos".
Monster-A-Go-Go is really something else; it's possibly the worst film which both HG Lewis AND Bill Rebane ever made, although the kiddie films Lewis made are supposedly even worse.