PASADENA, CALIF. -- My doorbell rang one recent morning. When I opened the door, I got a surprise, as well as an unexpected introduction to a question now troubling Congress and the American immigrant community.

Standing on my porch was Esteban Martinez, a man who had saved me a great deal of strain since I arrived in Pasadena in 1980. I had never owned a house before, and although I enjoyed looking at my newly acquired lawn and surrounding greenery, the idea of spending hours each weekend taking care of it filled me with dread.

Martinez -- we usually called him Stephen -- had kept the lawn mowed and healthy for the previous owners. He lived a few blocks away, had many other customers in the neighborhood and charged a reasonable fee. I hired him gladly but did not talk to him much after that. My wife was the family gardener, and my Spanish was far too rudimentary for useful conversation.

When the Immigration Reform and Control Act of 1986 was passed and I began to write about the new amnesty program for undocumented workers, I wondered briefly if Martinez might fit in that category. I quickly put the notion aside. Americans, unless it is their job or legal obligation to do so, do not ask such questions, particularly of people who, like Martinez, are so vital to life as we know it.

The period for filing amnesty applications began May 5, 1987. As someone who had employed him since 1980, I could certify that he had lived in the country continuously since Jan. 1, 1982, the crucial qualification for legal status under the amnesty. People who did not apply by May 4, 1988, would lose their chance. When Christmas passed and I heard nothing from Martinez, I assumed he was legal or had taken care of it some other way.

When Martinez appeared at my door this year with a pregnant young woman who spoke good English -- his nephew's wife, it turned out -- I was befuddled at first. Had I done something wrong? The young woman explained: "He is applying for the amnesty. Could you write a letter?"

I smiled with relief and congratulated him on his good sense. But I wondered: Why had he waited so long?

This is a question occupying the minds not only of Martinez's various employers, but of a significant portion of Congress and the assortment of immigrant-rights and other lobbying groups. All are watching the widening effects of the new immigration law with the wary intensity of people convinced that they are seeing a revolution but uncertain which centers of wisdom and power are being overthrown.

Will the new law bring all the eligible aliens into the sunlight, send the rest back where they came from and end a generation of subterfuge and paranoia? Or will the old fears of La Migra -- the Spanish nickname for U.S. immigration agents -- defeat the purposes of the law and leave a still large and growing underground immigrant population?

In the first eight months of the year allowed for amnesty applications, more than 1.2 million people applied. There is heated debate over how many eligible aliens remain. No one really knows, although many estimates suggest that as many as 800,000 may be hanging back.

Rep. Charles E. Schumer (D-N.Y.) and Sen. Edward M. Kennedy (D-Mass.) have submitted bills to extend the application deadline to May 4, 1989. Schumer argues that the Immigration and Naturalization Service, because of computer problems, moved too slowly in processing early applications and mailing official residence cards to applicants so their immigrant neighbors could see that the process worked.

Without that assurance, he says, people will not apply, thus the need for more time. Jerry Tinker, staff director of the Senate Judiciary immigration and refugee affairs subcommittee, said he has urged the INS to accept signed declarations from amnesty applicants that they will file their papers within a year of this year's deadline and thus remove the need for a new law.

Supporters of the current deadline argue that people are hesitating not because of fear but simple procrastination. "They have to get their papers together," said Patrick Burns of the Federation for American Immigration Reform (FAIR). "They have to get the money, but it's Christmas, and they first want to buy that bike for Mikey. It's the same reason you wait to pay your taxes until the last minute. The immediate always takes precedence over the important."

Amnesty programs in Canada and Europe have noted a flood of last-minute applications, as many as 10 percent of the total in the last day. Some officials suggest that many undocumented aliens may realize that the minute they obtain official status, they will have to start paying taxes, and they see no reason to rush it. Also, out-of-pocket costs can run into hundreds of dollars.

INS spokesman Duke Austin said talking about extending the deadline will confuse applicants. An extension, he said, would reward procrastination and threaten the program's legal commitment to pay for itself, without extending the program's benefits to a significant number of people.

When Martinez returned to claim the letter I had written for him, I asked him why he had waited so long.

He had crossed the border from Mexico in 1974, following his older brother. In 1975, he returned to marry and brought his bride, Margarita, back with him. Since then they have had four sons -- Juan, Angel, George and Steve -- all U.S. citizens, all fluent in the language and lore of America. They were an established American family, solid citizens of their community.

Martinez understood the new law well. He had read a pamphlet distributed at the local Roman Catholic church, St. Andrew's. The notary helping him with his application had explained things. He had worried about drunk driving citations in 1976 and 1984, but learned that they posed no problem.

So why did he wait? Martinez smiled and shrugged, as if to say: Why not?

"My brother and I thought we would just wait until the beginning of the year," he said. "We had things to do. The new year would be a good time for it."

Perhaps there was more to it, but I saw no need to pry. Margarita and Esteban Martinez smiled at me. One of their boys, sitting on my couch, had fallen asleep. It was time to go. I looked out the window at my lawn, pea-green and neatly trimmed. They were happy, and so was I.