''La Opinion, buenos tardes.''m The bustling operators at the high-tech offices of this daily newspaper answer in a hurried, professional way, throwing an English-speaking caller into a helpless stammer. Upstairs, publisher Ignacio E. Lozano has the conservative, impeccable look and bearing of a diplomat as he explains that the Spanish-language Los Angeles newspaper - founded in 1926 by his father - has grown in circulation from 22,000 in 1975 to 60,000 now.
La Opinion is the staid, respected flagship of a fleet of Spanish-language news media beginning to come into their own in Los Angeles.
The explanation is simple: Advertisers - especially of consumer goods - have awakened to the buying power of the Hispanic market and have looked to the Spanish-language media to carry their ads.
The upshot is that someone who speaks only Spanish and lives in Los Angeles can read a daily local newspaper (as well as a neighborhood weekly in many areas), watch television that includes local news shows, listen to at least half a dozen radio stations, and read at least one locally produced, general-interest magazine - all in his native tongue.
On the surface, this trend may appear to reinforce the idea that Hispanics are resisting assimilation into America's mainstream. But this may not be the case.
The feeling is spreading that advertisers have misread the Hispanic market. Big advertising agencies have approached Hispanics through the Spanish language. Yet, according to some market researchers, most Hispanics no longer use Spanish as their primary language.
Marketing vice-president Robert Molino of Linda's Mexican Foods talks of the ''phantom 54 percent,'' those Hispanics who primarily speak English.
''That's the group that has been ignored. They're the affluent ones,'' he says. ''That's the group that has gone to college.''
It will take about five years, speculates Hispanic Business publisher Jesus Chavarria, to put to rest the notion that the Hispanic market should be reached in Spanish.
The Spanish-language television network SIN, based in New York, has perpetuated a myth, says Kirk Whisler, publisher of a bilingual magazine, Caminos. Mr. Whisler urged the formation of the National Association of Hispanic Publications earlier this year, and he hopes to combat that myth: that Hispanics generally don't spend much time reading and prefer to speak (and watch television) in Spanish.
Whisler quotes a study by the California attorney general's office in 1977 that found that 34 percent of this state's Hispanics speak and read only Spanish , 12 percent know English but prefer Spanish, and the remaining 54 percent prefer English.
The story of the magazine Caminos, now in its fourth year of publication, is a history of the rise of Hispanic media. In its first year of test issues, 1978, it sold one or two national ads. The next year, three or four. Perhaps 20 in 1980, according to publisher Whisler. This year, he says, the magazine will probably carry more than 130 pages of national advertising.
The 12 Caminos employees work out of offices in a Salvation Army home for unwed mothers on the east side of Los Angeles. Already it is the largest bilingual magazine in the country, with 45,000 circulation, and Whisler hopes to break even with it next year. Since he began creating Caminos in 1976, Whisler has seen more than 150 Hispanic magazines come out and go under. But each year five or six that start publication still are surviving.
Newspapers have fared better. At least every other week, he says, another Hispanic newspaper starts publishing that will ''be around awhile.'' There are some 500 around the country already, although the majority are either in English or bilingual.
''The market is so big that we're not competing,'' says Whisler. ''There's a void to be filled. We're not elbowing anybody.''
Caminos publishes its major articles in two languages, but its lead language is English - 85 percent of the magazine's readers read it in English first. Spanish readership grows as copies are passed to parents and grandparents.
But the business aspect is only part of the story. Spanish-language media, especially KMEX, claim a unique, family-style relationship to the Latino community here. KMEX, the major local Spanish-language television station in the area, has gone from a black-and-white station employing 29 in 1972 to broadcasting in color with a staff of 130 today. Its ratings are competitive in some time slots with network affiliate stations.
''How often do you hear a station referred to as 'our' Channel 34?'' asks Danny Villanueva, KMEX's general manager. Mr. Villanueva, another businessman acknowledges, is an ''unofficial patronm of the community.''
A former professional football player, Villanueva has involved the station in all aspects of community life, from using the building as a service center for Guatemalan earthquake victims to hiring a lawyer to help fight passage of the Simpson-Mazzoli immigration bill. Just last week, Villanueva says, a runaway appeared in the lobby. KMEX was the first place he thought to come to when he left home.
The three hours a day of news on KMEX, Villanueva says, is not unbiased at all, but advocates issues important to the community such as bilingual schools and citizenship drives to get out the vote.
Kirk Whisler speaks for most in the Hispanic media when he explains, ''The community has identified its problems. The traditional media has done a nice job of focusing on the problems the community is having.''
His editor, Katharine Diaz, continues: ''We're trying to look at the positive things, not to whitewash anything, but to show what's going on to solve problems.''
Danny Villanueva counters the view that his Spanish-speaking audience is mostly immigrants, that American-born Hispanics prefer English.
''I think we're over the hill. I was the transitional generation. I was the one that tried to put distance between me and my parents' culture. . . . I was an English teacher. I had to go back and learn my language as an adult,'' he says. ''We're not running from our culture anymore.''
Ignacio Lozano of La Guardia sees limits here. ''It's logical that Mexicans want to preserve their heritage. But I don't think anyone seriously thinks other than that English is the national language. All the economic wherewithal lies with Anglos, and I really don't see any trend in any other direction.''