The new idealism of the 'melting pot' - blending Americans of all ages

Every weekday morning, children walking to the Madeira Beach Elementary School pass a large condominium complex, its tan stucco buildings rising dramatically out of the flat Florida landscape.

Between the sidewalk and the sprawling grounds stands a five-foot-high wall, its length broken only by a guarded entry gate. Occasionally the students pass a condominium resident out for an early walk, but for most of them the sidewalk is as close as they come to the world inside that stucco wall - a world where no one under 18 can live permanently.

This adult community, home to some 1,200 residents, is one of a growing number of age-restrictive developments across the country. Once scorned by social scientists as ''geriatric ghettos,'' these complexes are enjoying widespread acceptance and popularity as the number of Americans over 65 increases.

According to one estimate, 10 percent of the nation's older people now live in housing that bans children. Another 20 percent might choose age-segregated buildings if funds and facilities were available, says Charles Longino, director of the Center for Social Research and Aging at the University of Miami.

Page after page of real estate ads in Sunday papers here describe the advantages of an ''active adult life style'' - privacy, security, friendship, serenity. The operative word is active, with color photos showing mature couples enjoying golf, tennis, swimming, and parties.

Yet this senior-citizen version of Eden is not always as idyllic as developers would have prospective residents believe. Increasingly, the legality of adults-only housing is being challenged, with charges of discrimination flying through the semitropical air like volleyballs on a Florida beach.

Opponents charge that families with children are being denied equal access to housing. Proponents counter that these communities are, in effect, clubs, whose members agree to certain conditions and restrictions before moving in.

In one highly publicized case in Broward County, a young couple faces eviction from their home in an adult neighborhood because of the birth of a daughter. Ronald and Bonnie Pomerantz, parents of 11-month-old Ericka, have vowed to fight their case ''for every family who has children.''

Beneath the legal complexities lies a broader social question: Can we afford to become an age-stratified nation - the old sequestered in Sunbelt condos and mobile home parks, the young only grudgingly accorded visiting rights? What price will both generations pay if each becomes fearful and resentful of the other, thereby perpetuating everybody's stereotypes and worst fears?

The questions deserve careful consideration in light of current demographics. For the first time there are more Americans over 65 than there are teen-agers. The elderly population is growing twice as rapidly as America as a whole, according to census data, and by 1990 the number of people 65 and over will increase by nearly 32 million. By the end of the decade there will also be 3.3 million more children under age 6 - a 17 percent increase.

To some observers, the adults-only debate presages a larger, more complicated balancing act. Younger people will need education and job training, older people social security and medicare. Determining priorities for limited federal funds could become a major issue of the '80s.

The housing debate also raises another, less obvious question: In pitting the world of Lawrence Welk against the world of Michael Jackson, are we denying both groups full participation in society?

Retirement communities serve many good and legitimate purposes, as those Sunbelt real estate ads point out. But what an incalculable loss to society if more than a quarter of the older population eventually chooses voluntary exile in single-generation living - if retirement becomes, in effect, a separate country.

The ''melting pot'' has long been a concept at the center of American democracy, signifying the faith that a fusion of many races could only invigorate the nation as a whole. In the '80s, perhaps the term ''melting pot'' will take on a second meaning to affirm that Americans at all stages of life will benefit from melding together - the young, the retired, the in-between. Will there be adjustments? Of course. But without this blending of the generations, this extending of the family, a richness will be sacrificed in everybody's experience - both inside and outside of those stucco walls.