Downstairs at the Californian Steak House on 14th Street NW, the thin blond go-go dancer has stripped off everything but her gold high heels and is lying on her back, gyrating to disco music and the pulse beat of red lights.

Upstairs, in a cramped office lined with cases of liquor, her boss, Quy Huy Nguyen, is wearing a three-piece blue pin-striped suit and leaning back in a swivel chair. He smiles broadly and says, "A half-million dollars. . . . It'll take a half-million dollars to buy me out."

Mr. Quy, as he is called, then breaks into a hearty laugh, the barrel-chested laugh of a man who runs a profitable business and holds a six-year lease on one of the more valuable chunks of real estate in downtown Washington.

Quy, who said he used to operate a bar in Saigon, is now one of the combatants in a behind-the-scenes economic battle being fought along the so-called Strip of lower 14th Street NW between H and I streets, where more than a dozen sex-oriented businesses offer neon invitations to a steady stream of men.

It is a big-money contest -- fought at negotiating tables and sometimes in courtrooms--between people who make money selling property and people who in many cases make money selling striptease, massage and "marital aids" and other things.

Big developers were supposed to win the battle quickly and wipe out the Strip, tearing it down to build new office towers. But the Strip is proving much more resilient than expected, judging from interviews with 14th Street business people, property owners, real estate agents and developers.

The object of the battle is land, which has skyrocketed in value as the downtown office building boom has spread toward the Strip. The planned development around Metro Center, only two blocks away at 12th and G streets, has made the Strip more attractive, as has the proximity of the new D.C. Convention Center under construction near 11th and I streets. Those, plus the McPherson Square Metro entrance at 14th and I, have helped turn 14th Street property to gold.

At 14th and H, the National Food Processors Association paid $9.8 million for a parcel in October 1980, paying $530 per square foot, a Washington record that stood until last April when Daon Development Co. of Canada spent $40 million-- $615 a square foot--for a site at 13th Street and New York Avenue.

The lower 14th Street area already has been partially transformed from high-excitement to high-rise. Where the Merry-Land Club once pounded with striptease music at 14th and L, for instance, a new office tower owned by the American Medical Association stands ready to open.

Eleven similar buildings are already in various stages of design and construction within a block of the Strip, meaning that for some years to come, lower 14th Street is likely to be the site of some strange encounters: the well-heeled meeting the scantily clad high-heeled.

For example, the National Association of Realtors last year moved into a renovated building which it bought for $8.2 million at 777 14th St. NW. Directly across the corner from the Realtors is a sort of sexual shopping center offering "adult" movies, books, baths and marital aids, along with "international hostesses" and "fun."

The heaviest concentration of striptease and pornography has remained largely intact between H and I streets, and this last hurrah of one of Washington's most colorful and controversial spots may drag on for years, with some real estate sources estimating it may take up to a full decade to "purge" the area, as one developer put it.

The neighborhood wasn't always like this. In its heyday earlier this century, fashionable residences lined K Street on both sides of 14th. Streetcars carried well-dressed Washingtonians down 14th Street from such places as Chevy Chase and Mount Pleasant to downtown's prime spot for high-class nightclubs, top-flight restaurants and clothiers, and movie houses like the now-demolished TransLux.

But as the city center declined in the late '50s and '60s, so did many of 14th Street's businesses. The slide reached bottom in the vandalism, looting and arson of the 1968 riots.

In the past two decades, more and more businesses shut down or moved away, and, in their place, honky-tonk became dominant. Some of the remaining restaurateurs saw more money to be made by ripping out their booths and building stages for striptease--a move that Quy, for instance, made just a year ago after three years of running a regular restaurant.

Quy is currently a player in the most active property struggle on the Strip. He is guarding his Californian Steak House against a prominent Washington developer, Jeffrey N. Cohen, who is the only developer to have made any headway in the block between H and I streets, according to real estate sources familiar with the area.

Cohen has spent three years and more than $1 million buying property around the Strip, including the Parkside Hotel on I Street and the Californian's premises at 829 14th St. NW, for which he paid $315,000, according to city land records.

As the new owner of the Californian, Cohen then sought to buy out Quy's lease so he could tear down the structure and build in its place another new commercial building, according to Quy.

After Quy refused two offers, Cohen filed suit in Superior Court in February 1981, seeking to evict Quy on the grounds that nude dancers violated the lease, which runs until Jan. 1, 1988, according to court documents. The case is pending.

The battle between Quy and Cohen illustrates how hot a property lower 14th Street has become. Their protracted struggle also shows in part why the Strip has not disappeared as quickly as expected.

Quy's lawyer, Christopher Teras, said in court papers that the conflict between Cohen and Quy involves "hundreds of thousands of dollars," and suggested that Cohen's court action was part of a campaign to drive Quy out of business because the land is so valuable.

Cohen either owns or has options to buy a sizeable chunk of land on the southeast corner of 14th and I streets, according to land records and real estate agents who have studied the area. They say Cohen's plans for an office tower are stalled until he removes Quy, plus Benny's Home of the Porno Stars and a Popeye's Fried Chicken outlet.

Meanwhile, persistently high interest rates and a recent tailing-off in new office development suggests to some knowledgeable real estate sources that development along the Strip may be pushed back a few more years.

Cohen did not return repeated phone calls. His spokesman, William J. Wolfe, explained, "I am not sure that Mr. Cohen wants his interests on 14th Street written up in The Post." Cohen's lawyer, Leonard Collins, said his client took the court action "because we want to improve the neighborhood."

A problem for Cohen and other developers who might like to build on the Strip is that the land is mostly a crazy quilt of small lots, several of which must be bought to assemble a parcel large enough for a major office building.

Complications often arise. Camden Company, a general partnership represented by attorney Orie Seltzer, paid $650,000 to buy the property of Benny's Home of the Porno Stars at 829 14th St. NW in February 1981. To do that, the partners had to buy out 10 heirs, scattered from Hawaii to Florida to metropolitan Washington, who inherited the property from a family who had owned it since the Strip's earlier days.

For developers seeking to buy along the Strip, further complications often arise because most of the sex-oriented businesses rent, rather than own the existing buildings, so would-be developers must arrange to buy out both property owners and leaseholders to take over property.

Another reason the Strip endures is that it makes money, apparently a lot of it. Its operators would probably not be able to make nearly as much money anywhere else around Washington, primarily because a 1977 city zoning law limits sex-oriented businesses to commercial zones, and within those zones prevents them from locating near each other.

The measure was aimed specifically at banning a new Strip anywhere in D.C. Operators along the Strip said these businesses tend to flourish when situated in a cluster.

Benny's, formerly Benny's Rebel Room, is perhaps the best known of the Strip's clubs. It is now operated by Roger W. Simkins Jr., 35, who currently faces gambling and weapons charges in the District. Simkins was acquitted in 1980 on federal charges that he ran a multi-million-dollar interstate gambling ring.

Around his neck, Simkins wears a $20 gold piece that belonged to his late father, Roger (Whitetop) Simkins, one of the city's most prominent gamblers. Simkins has had the gold piece redesigned so that a gold shark's head, with teeth bared, protrudes from the coin.

Unlike the operators of clubs on either side of him, Simkins holds only a month-to-month lease and could easily be forced out by a new owner of his building.

In a recent interview at Benny's, while a dancer stripped and simultaneously a pornographic film was being shown, Simkins said he was considering leaving the business because it brings with it "an awful lot of aggravation and a lot of peculiar people."

Minutes later, U.S. Park Police in plainclothes entered Benny's to arrest two young men on charges of selling marijuana at nearby Franklin Square. Simkins said he doesn't allow such illegal activity on the premises.

Down the street from Benny's, a large neon butterfly flaps its wings, inviting patrons to the Butterfly Club at 823 14th St. NW. On a recent weekday night, despite a steady chilly rain, many men answer the butterfly's call.

Inside, at 7 p.m., nearly 75 men, most of them sitting alone at their tables, are watching a succession of strippers perform on a mirrored stage under red lights. At the same time, a large video screen is showing a grainy black-and-white silent film of sex acts.

As they watch, the men are keeping three waitresses very busy, ordering beers and drinks for $2 and up. A few hundred men, in all, are spending money on the Strip this cold rainy weeknight, some circulating from club to club to massage parlor to bookstore.

The Butterfly itself has entertainment in several different locations. Upstairs is a second bar, the Cocoon, which shows pornographic films in color, with sound.

A sign in the hallway outside the Cocoon advertises nude hostesses on the third floor. On this night, three women in the third-floor waiting room are wearing black negligees and offering massages, but no prices are posted.

"Business has never been better," said Abraham Zaiderman of Potomac, president of K & B Enterprises, which operates the Butterfly. "Anybody who wants to buy out this block, if he has the money, he'd better have a lot of money."

As he spoke, Zaiderman sat behind the desk of still another business located in the Butterfly building, a second-hand store that trades in used merchandise and advertises that it buys and sells gold.

"I have more confidence than the rest of these people" on the Strip, Zaiderman said, estimating that businesses there will remain for at least five years. He said he has almost four years remaining on his lease and has no plans to sell out unless someone offers big money.

The owner of the Butterfly property is Emanuel Koroulakis, a Washington restaurateur who said he bought the 72-year-old building in 1960 to open the Taverna Romana, a restaurant that he closed after the riots.

Koroulakis, who owns restaurants in northwest Washington and Arlington, said he recently has had a number of offers to sell his 14th Street property, but rejected them because of K & B's lease and because he is not desperate for money.

"I haven't been back there in years," said Koroulakis. "What they do inside the Butterfly I don't know. I just collect my rents." He joked that he believed his priest would not approve of the entertainment that the Butterfly offers, but said K & B is nonetheless a good tenant.

Across from the Butterfly, a visitor opens the front door of the "Paradise Escort and Model Service." Inside, six young women who had been sitting on couches and watching television, suddenly stand at attention. Leotards are the dominant form of dress. They ask the visitor whether he has ever been to Paradise before, then ask if the visit is business or pleasure.

Instead of X-rated movies and $30 fees, the conversation this time turns to real estate and the prospects that the Strip might someday soon have to move. It is a subject with which some of the women are quite familiar. "We've been hearing that for years," said a dark-haired woman whose purple eye shadow matched her leotard.

"But nothing ever happens."