Their U.S.-born daughter, Damaris, 20, however, speaks primarily English with her friends, at college in Azusa and at her seasonal job at Disneyland. She values her bilingualism but said growing up in the U.S. has made her more articulate in English than in Spanish.

A study released Thursday by the Pew Hispanic Center, a project of the Pew Research Center, reports that in families like the Peredas, for whom Spanish is the dominant language among immigrant parents, English fluency increases across generations. By the third generation, Spanish has essentially faded into the background.

Hispanics recognize learning English is key to economic success, according to the study, which was based on survey data collected between 2002 and 2007.

"The ability to speak English is a crucial skill for getting a good job and integrating into the wider society," said D'Vera Cohn, a senior writer at the research center, a nonpartisan research organization that does not advocate immigration policy. "Language is a vehicle for assimilation."

Though findings echo the history of immigration waves in the U.S., experts said, they counter the widespread perception Hispanic immigrants do not assimilate and their large numbers are a threat to the English language.

"People get very upset about 'Press 2 for Spanish,' " said Rubén G. Rumbaut, a UC Irvine sociology professor who has done his own research on the language issue.

But "there is no way English is being threatened by immigrants. . . . The switch to English is taking place perhaps more rapidly than it has ever in American history."

English fluency has long been at the center of the immigration debate in Southern California and around the nation. At the city and state levels, language battles are being fought over school tests, storefront signs and local ballots. In Congress, legislators recently sparred over sanctions against employers who require workers to speak only English.

Groups that support controls on immigration and English-only initiatives say the federal government and U.S. companies are making it easy for Hispanic immigrants to continue to speak Spanish.

According to the Pew report, which analyzed surveys with more than 14,000 Hispanic immigrants, only 23% of adult first-generation Hispanics say they can carry on a conversation very well in English, compared to 88% in the second generation and 94% in the third. Mexicans are the least likely to say they speak English well, which the study's authors attribute in part to a lower educational level.

The Pew analysis found that 89% of Hispanics recognize they need English to succeed in the United States, while 46% of respondents this year said language is the leading cause of discrimination against them.

Salvadoran immigrant Manuel E. Mancía, 39, said he wakes at 5 a.m. each day to study English before going to a Hollywood day laborer center to wait for construction work. Occasionally, he attends an English class at the center.

Though Mancía said he has learned enough in the last six years to communicate with some employers, he believes he could get more and higher-paying work if he were fluent.

"I have lost job opportunities because I don't speak English," he said, citing one job that promised $15 an hour for several months. "Those opportunities don't come up often."

According to the Pew study, immigrants are more likely to speak English very well if they are college-educated, arrived in the U.S. as children or spent many years here.

Similar studies have also concluded that immigrants' native languages recede over generations. Rumbaut co-wrote a study released last year that said Mexicans and Central Americans retain their language longer than Asians and white Europeans but that even among Mexicans, 96% of the third generation prefer to speak English at home.

"Like taxes and biological death, linguistic death seems to be a sure thing in the United States, even among Mexicans living in Los Angeles," Rumbaut's study said.

Johnny Rodriguez, 27, came to the U.S. from El Salvador when he was a baby, graduated from Long Beach State in 2003 and speaks both English and Spanish fluently.

Growing up, Rodriguez said, he often interpreted for his parents, who didn't speak much English. His father is a carpenter and his mother is a retired nanny.

"I felt they were put at a disadvantage," he said.

The Pew analysis also reported that 44% of Hispanic adults are bilingual. In the workplace, 28% of Hispanic immigrants speak only Spanish and 24% report they speak English and Spanish equally.

For Rosa and Manuel Pereda, Spanish is essential at work. Rosa sells cemetery plots to Spanish-speaking families and Manuel, a school bus driver, speaks English to the teachers and children but Spanish to parents.

The Peredas say life now, compared to when they arrived in the U.S., is much more accommodating to Spanish speakers. Except at some medical and government offices, a Spanish-speaking employee can almost always be found, they said.

"It's changed," Manuel said. "Now Spanish is spoken every where."

Both said learning some English has been a struggle, in part because they arrived as adults and had little education back home.

Often, Damaris and her siblings correct their parents' grammar and pronunciation in English. Rosa Pereda said she and her husband are both determined to keep practicing.

"I am not thinking of leaving this country," Rosa said, "so it's better I understand the native language."