For decades, Falls Church residents and city planners have been debating about what to build at the intersection of Broad and Washington streets, the center of what they hope will be a revitalized central business district.

Past efforts to erect a 12-story office building on the southwest corner were defeated by city opposition to high-rise structures, and plans for a retail and office complex fell victim to the recession.

Now, a Vietnamese family believes it has the answer for that corner in the form of a shopping, restaurant and office complex emphasizing international foods and goods.

Nguyen Van Minh and his wife, Nguyen T. Bach Luu, owners of a food and department store on Wilson Boulevard in Arlington and the Mekong Restaurant in Tysons Corner shopping center, bought the property last month from Falls Church developers Ross Keith and Alexander Feldman.

The 116,810-square-foot parcel of land was assessed by the town of Falls Church at $767,000. A reliable source said the Vietnamese couple paid about $850,000 for it.

The Minhs, along with other family members, plan to build a three-story, 80,000-square-foot complex dominated by international restaurants and shops, both Oriental and European, according to N. T. Hung, a Howard University economics professor and a consultant to the family. Surface parking space for about 260 cars is planned.

The Vietnamese owners are counting on the estimated 30,000 Asian residents of the Washington area to form a nucleus of customers. They hope the center's international flavor will attract members of the diplomatic and international business community.

In addition, Hung said the 1980 census showed that a population of 150,000 highly educated, affluent people live within a five-mile radius of Falls Church, making the area a "tremendous" market.

A sign now standing on the property says it is the site of the Mekong International Center, but Hung said the family has not made a final decision on the name. Minh believes the center should have a familiar American name to broaden its appeal, and would like to call it the Falls Church Center. But his wife believes the name Mekong is lucky for her because of the success of the family restaurant and food store.

The Minhs reportedly expect to spend about $4 million on the project. They will move their food and department store from Wilson Boulevard to the new complex, and are now seeking other anchor tenants.

They say they hope to find tenants and line up financing in time to start construction by the middle of 1983, with completion scheduled for 1984.

"It's the best piece of ground in Northern Virginia. I just couldn't hold onto it any longer," Keith said of the property.

He said he bought the land "about four years and a quarter of a million dollars' worth of interest ago." After spending $155,000 for architectural drawings of the seven-story, 143,280-square-foot retail and commercial building he planned to name the George Mason Plaza, Keith said he was overtaken by the real estate slump and high interest rates.

Keith and his partner, Feldman, bought the property from the First Virginia Bank at a time when land prices in Falls Church ranged from $4 to $5 per square foot.

About 10 years ago, the bank tried to build a 12-story office building on the site. City legislation to change the seven-story height limit in that section of Falls Church was proposed at the same time the bank applied for city approval for its building plans, said Mayor Carol W. DeLong.

"After much public debate the application was withdrawn and the ordinance to change the height limits was never adopted, and the height limitation has remained in effect to this day," the mayor added. "In my estimation [the height limitation] is firmly supported by the citizens of the city."

Keith said his firm has remodeled several houses he owns on the opposite corner of the intersection, at a cost of $700,000. The buildings are fully occupied by tenants that include a bank, a hairdresser, attorneys, real estate brokers and a pet shop. They pay rents of $11 to $14 per square foot, which are about average for the area. Despite the full house, though, Keith said his company is "still on a construction loan, and we show a deficit every month."

Keith said, "There is still no commercial money on the market." He said that if the recession eases, he hopes to start work next spring on a shopping center called Independence Square on that location.

Mayor DeLong said an international center such as the Minhs envision "might be pleasing to the city." She added, however, that "since we do consider that our central business district and while we want something to conform to our ordinance, I don't think we want something totally unprepossessing. We could not argue with something at the height limit," she added.

The Minhs believe their plans are far from "unprepossessing."

An atrium with gardens and fountains is planned for the structure's plaza level, on the ground floor. Around the atrium will be a series of stalls selling international foods. Customers will buy food at the stalls, then carry it to tables near the gardens and fountains.

The Minhs think they can "provide high quality food at affordable prices" because waiters will not be needed, said Hung. Other floors will be devoted to shops, restaurants, movie theaters and offices. They hope to meet the needs "of the typical shopper," with food, entertainment and stores, Hung said.

In planning the center, the Vietnamese owners will try to assure that the building "blends with the beauty and historical character" of Falls Church, he added.

The Minhs fled Vietnam with their nine children at the end of April 1975, the day before the Communists took power in Saigon. Since arriving here, the family reportedly has become one of the most successful in the area's Vietnamese community.