Pasco County, Fla. — The counter at Hannah Ingentio's bike shop in Holiday, Fla., has taken on something of the character of the cracker barrel in a village general store. And in its own small way, it is a bridge that helps residents of this county cross what appears to be a yawning generation gap.
''This is where everyone meets,'' says Mrs. Ingenito, who owns Wheel Power with her husband, Ralph. Young cyclists can be found swapping ideas on equipment with senior citizens, she explains. As she chats with a visitor, an elderly resident brings in a flat tire for repair while a teen-ager tries some new pedals on his bicycle.
The majority of her customers are retirees. Sturdy-looking adult tricycles, often equipped with baskets for hauling groceries, outsell 10-speed bicycles, popular with the younger set, by 4 to 1 at this shop.
To a large extent, retirees and the young still live separately and have little contact in this rapidly urbanizing retirement county. But that is changing. Although the number of retirees moving here continues to soar, more young families are moving here to fill jobs required to meet the needs of the older set.
''Somebody's got to build the homes, handle the dry cleaning and air conditioning,'' says Mike Rapp, director of research for the Pasco County School Board.
As a result, the young and retirees are beginning to mix more, in schools where retirees do volunteer work, in neighborhoods, and at places like Wheel Power.
In conversations with retirees, teen-agers, and community activists here, one finds:
* Retirees volunteering as grade-school teacher aides.
* Some retired families who have chosen to live in neighborhoods with children, rather than in the more age-isolated retirement communities that are still available here.
* A high school counselor trying to help students better understand the elderly.
* Families with teen-age and younger children living in what were once almost entirely retirement neighborhoods. Often the homes, built for retired couples, are small for families with children. But they are affordable. Some friction has arisen, but teen-agers and senior citizens tell of many instances of friendships with their new neighbors.
Flexibility on the part of the young and old is helping residents of this county adjust to the increased presence of younger families, says Carol Keyes, a specialist on aging employed by the District School Board of Pasco County. Flexibility is a quality other communities, especially in retirement areas across the United States, are increasingly likely to be called upon to exercise, she says.
The latest Census Bureau data shows the number of persons in the United States 65 or older increased from 11.3 to 11.7 percent between 1980 and 1982. The median age increased from 30 to 30.6 in that time. These figures, demographers say, show further evidence that the US population is gradually but steadily aging.
In Florida, more than 17 percent of the population is already 65 or older. In Pasco County, one out of three persons is 65 or older.
As the southern coastal regions of this retirement state became more and more expensive, newcomers began settling farther north. In the process, this once-rural Gulf Coast county grew from about 76,000 in 1970 to about 200,000 today.
Retirement subdivisions sprang up all over the county. But increasingly younger families are moving into such communities.
The number of public school students in Grades 1-12 increased from 14,099 in 1972 to 24,813 in 1982, says Mr. Rapp of the Pasco County School Board. Public recreation - mostly golf and shuffleboard - was designed largely for retired persons, he says. There is ''very little'' for children, he adds.
Instead of complaining about the growing number of children here, some retirees have gone back to school - as volunteer teachers' aides.
Sitting at a small children's table in the Anclote Elementary School here, several of them explain why.
''I come to school and sometimes they (students) hug me and kiss me,'' says Betty Solomon, a retiree from Teaneck, N.J. ''I sit right at this table,'' she says, where she helps students with math and reading several hours a week. ''I get birthday cards and Valentine's Day cards from them.''
Herb Groelinger, a retired plumber from New York, says: ''It's not a question of giving; we're getting, too.''
Some 100 volunteers, about 35 of them retirees, logged some 8,000 hours of help at the school during the past year.
Narrow streets and small yards are common here. It poses special problems - or opportunities to get to know your neighbors, depending on your view, as several ninth graders explained during a round-table discussion at their school.
Alisa lives in a home with retired couples in houses on either side. The man on one side frequently complains about the noise her bird makes, and tells the family to shape up its lawn. ''If I throw something on his lawn, a baseball, he gets so mad,'' she says, adding that even candy wrappers make him mad.
But the other neighbor, a couple in their 70's, are friendly, and often ''come over with baking and stuff,'' says Alisa.
Almost all the students had similar mixed tales. Young and old get along better ''if each side cooperates,'' says Pilar, one of the students. Their counselor at Gulf Junior High, Glenn Cable, offers the students several hours a year of training in how to better appreciate the elderly. He says he tries to help them be tolerant, to forgive, and understand the challenges of aging.