Ship of Monsters (Mexico) a.k.a. La Nave de los Monstruos

The plot apparently involves a two-girl rocket from an all- girl planet. One girl decides to betray the other and release four monsters to attack the Earth. Also on the rocket is a powerful robot whom each girl tries to use against the other. In Mexico , these aliens encounter a cowboy guy and his young cowboy son. The sets, costumes, and special effects are very cheap, but no cheaper than those of the average American B-movie of the time. And unlike some of those silly American productions (Giant Claw comes to mind), "La Nave de los Monstruos" was clearly made with a sense of humor throughout. The four monsters (a big-headed goblin, a hairy beetle, a cyclops, and a skeleton) are fascinatingly ugly. The girls wear tights and bathing suits both inside and outside the spaceship. The robot makes endless beep-beeps. The cowboy guy sings and dances. Scene after scene is pleasingly puzzling.

Goldweber, David Elroy (2012-06-14). Claws & Saucers: Science Fiction, Horror, and Fantasy Film: A Complete Guide: 1902-1982 (Kindle Locations 63352-63362). David E. Goldweber. Kindle Edition.