Sergeant Joe Friday has asked for "just the facts" in many ways over the years, but this month he'll try something really different: interrogating bad guys in Spanish.

Dan Aykroyd, the star of the "Dragnet" movie, hasn't transferred to Mexico City. But Hispanics in key cities north of the border can see a Spanish-language version of "Dragnet" on Home Box Office.Some HBO subscribers will be able to choose whether to hear a Spanish or English soundtrack to "Dragnet" and several other HBO and Cinemax features each month.

"There's a very large Hispanic population in this country, about 25 million people, which is equal to the entire population of Canada," said HBO Vice President Dick Beahrs. "Whereas many of them speak English as well as Spanish, many of them welcome the opportunity to use their first language."

To hear the Spanish dialogue, a viewer must subscribe to a cable company using the Spanish audio track and, in most areas, have a stereo TV with a second audio program switch. A special audio decoder, costing between $45 and $70, can be added to sets that don't have the switch.

There is no extra cost for the Spanish-language feed.

Twenty-one cable systems in seven markets are taking the Spanish audio, with 20 more set to start before May, according to HBO's Concepcion Lara. On board are some systems in and around Los Angeles, San Diego, Dallas, El Paso, San Antonio, Miami and New York.

Besides "Dragnet", HBO's January Spanish lineup includes "Empire of the Sun," "Ishtar," "Jumpin' Jack Flash" and "Something Wild." Cinemax is screening "Close Encounters of the Third Kind" and "Indiana Jones and the Temple of Doom," among others.

Hollywood movies have been dubbed in Spanish before for Latin American and U.S. Hispanic theaters, usually months after their English-language premieres. Recently, more movies have opened in both Spanish and English simultaneously.

In 1988, about 50 Hollywood releases, such as "Oliver and Company," "Baby Boom," and "Willow," were retrofitted with Spanish sound by Intersound, said Garry Morris, a spokesman for the dubbing studio.

About 31 percent of the Hispanic homes nationally take cable, according to Miami's Strategy Research Corporation, compared to the 53 percent of Anglo households.

But that might not translate into a boon for HBO.