In the DVD commentary, director/writer Glenn Coburn freely admits that he made a bad movie. In fact, he wanted to make a bad movie, as an homage to the other bad movies that somehow still got remembered. According to him, the list of things that a bad movie must have are 1) evil invading aliens, 2) ivory tower scientists who want to study the aliens, 3) an obsessive military who wants to destroy the aliens, and 4) a young couple in the middle of it all who is just trying to stay alive. Oh, and 5) a topless scene. The movie does in fact have all of these things, so in that he succeeds in making a "bad" movie.
Despite that, I liked this movie. Or maybe because of that. Many filmmakers who are aware that they're making a bad movie just try to have fun with it, and go for a goofy tone, and yet there is an earnestness to their goofiness that works against that purpose. Zombie Town was like that, where the filmmakers were aiming for quirky characters and witty lines, and ended up with an unremarkable movie. Bloodsuckers from Outer Space was so utterly without pretension, so rankly low-budget, that it had an undeniable charm.
The young couple trying to stay alive in the movie (Jeff and Julie, played by Thom Meyers and Laura Ellis) seem to be playing things mostly straight, but the characters that they're surrounded by are ridiculous. Jeff is a photographer/reporter who is having issues with his uncle, who wants him to give up his photography dream and become a dairy farmer. His uncle, and most of the other town residents, are bigoted and conservative, whereas Jeff is liberal and artistic, and wants to express himself. He meets Julie when she gives him a ride shortly after his own car breaks down. Julie, like all free-wheeling young women on the road, has a canister of nitrous in the back seat of her car, from which Jeff takes a healthy dose. The two of them get along just fine.
Although it's already begun, they have yet to realize that Jeff's town is being invaded by an alien life force, which takes over human bodies and causes massive internal hemmorhaging. The possessed humans vomit up most of their own blood, and then seek other living things to suck blood from to replace what they lost. The local research facility knows what's going on, but wants to research the aliens instead of warning the townspeople. The military finds out about the invasion, and the general in charge, General Sanders (Dennis Letts, who went on to play army commanders, judges, and CEOs for much of his career), wants to exterminate them all, at any cost.
If you can't appreciate the charm of a budget film, you will not like this movie. Even if you do have grade-Z movies in your collection, this one may not be quite to your taste. But I would say it's worth a shot, so if you have the chance, check it out.