How bad is it? In parts it's rather good, but most (especially 2nd half) is not.
Should you see it? If you can find it, yes.
Even if this weren't the only film ever done entirely in American Sign Language, it would be a weird movie. There's a teenage kid who goes from blond to dark hair, painted eyebrows, giant fake nose and taped-on widow's peak whenever he becomes a vampire, which he doesn't seem to remember, except in a flashback to when he was a child and ripped out the throat of a puppy (shown). Now he forces hippies who stab priests to crash their motorcycle with mind control, in between attacking women and getting transfusions from his father, a minister - who may or may not be his father, as his mother had an affair with Dracula. There's bumbling intentionally comedic policemen, a hunchback with tin cans for hands [I swear I'm not making this up] and, because of the sign language, a policeman who flaps his arms like a bird to explain away the vampire. For the hearing, there's an added audio track with three narrators, one for the vampire, one for female characters and one for everyone else. It's done very seriously, then has broad intentional comedy, then tries to return to seriousness, then goes all artsy and weird and 1970's. The black and white photography appears to have been a choice, rather than a budgetary necessity.