He pulls the strange-looking car over and asks the driver to step out. Under the streetlights, Valdez sees a silver-gray, multi-limbed, obviously alien thing gracefully unfold itself out of a cabin that looks impossibly large for the dimensions of the car, or spacecraft, or whatever it is. "I've discovered the first unidentified driving object," he thinks.
Not knowing what else to do, he starts to explain the no-cruising law, but the alien interrupts, apologizing. Its voice is surprisingly humanlike for such a different bodyform, and to Valdez's amazement, the visitor speaks... fluent... Spanish. The satellite TV feed the aliens learned English from happened to be Telemundo.
Fearing government agents wielding scalpels ("this urge to dissect one's guest seems unique to Earth," says an alien), Valdez does not report the incident, but instead clocks in early and listens to their story. War had ravaged the roads and destroyed the fast-food restaurants on their planet, so they searched for another place to cruise. In California, on a brightly lit night, they almost blended in.
As Earth soon finds out, however, their presence has awakened an ancient enemy, dormant for millenia beneath the Earth's crust. Repellently Lovecraftian monsters scrabble to the surface, devouring many people and leaving many survivors gibbering and insane. It's up to the Space Hombres, working with the best technology the US military has to offer, to devise a solution to stop the subterranean threat.
However, the movie is just not going their way; the monsters are too numerous, powerful, and intelligent. The film takes a mystical turn, however, when God arrives, and with the wag of a finger, turns the monsters into dust. His reasoning: if humans want to destroy their planet themselves, He won't get in the way (and hasn't in the past). However, humans vs. the underground monsters was not a fair fight, and He was forced to choose sides and end it.
"Hey, thanks, God," says the president, Valdez, and the Hombres as He disappears in a swirl of clouds and light.