How bad is it? It's a typical Jess Franco film, which is never a good thing.
Should you see it? Don't go out of your way, but yes, if it's at hand and you're bored.
The Killer Barbies were an actual band in real life and this film was meant to bring them greater notice (It didn't work. "Killer Barbys vs Dracula," a sequel, didn't help). A band gets stuck where there's a countess who stays young with a method that involves killing young people. There's plenty of gore and nudity, dwarves, cannibals, dummies used as dead bodies, unsuccessful day-for-night shots, no continuity and the film doesn't really go anywhere. Director Jesus Franco proves he can make films exactly the same in the 1990's as he did in the 1960's. Still, it's a much better title than usual and it's not unwatchable.