Perhaps they were only being polite guests, but members of the Democratic site-selection committee who spent three days touring Washington last week seemed to be taking more seriously than before the city's bid to hold the 1984 Democratic National Convention.

Only a month ago,committee members privately pooh-poohed Washington's chances for snaring the prized event its first time out. Many of them appeared to be gazing westward to San Francisco as the inevitable spot to choose and crown the next Democratic presidential nominee.

But those members seemed a little less certain of the choice last week, after sampling Washington's near-gushing hospitality and mulling over earlier vists to San Francisco, New York and Detroit. The committee still must visit Chicago next weekend before reaching a final decision April 21.

"It was a novel idea six or seven weeks ago to consider Washington," said William R. Dixon, the Wisconsin commissioner of banking and a member of a site-selection technical advisory committee. "Now it's a serious idea."

That sentiment was echoed by Ray Majerus, a union leader and chairman of the site-selection committee, and Richard J. Murphy, chairman of a technical advisory committee.

"All in all, Washington technically is stacking up exceedingly well," Murphy said. "Washington is very much in the running."

It hasn't hurt that Chicago is being wracked by a divisive mayoral campaign that has split the local Democratic Party or that San Francisco Mayor Dianne Feinstein is wrestling with political difficulties of her own. But Washington-area officials also made some compelling arguments in favor of the capital city.

The Democratic National Committee would save millions of dollars by holding the convention here. Washington's new 800,000-square-foot convention center could easily house the show. There are plenty of hotel rooms. Security is superb. And there's a lot to do and see here.

Committee members also were impressed by the regional flavor of the presentation, with Govs. Harry Hughes of Maryland and Charles S. Robb of Virginia taking part.

However, political considerations will weigh heavily on the final decision, and here Washington may have a less compelling case to make than some of its competitors.

Pamela Harriman, a leading figure in the national party and head of the city's host committee, contends that by holding the convention here, Democrats would be making a statement that the federal government isn't to blame for many of society's ills, as President Reagan has suggested, but that Reagan himself is the problem.

Detroit officials argue the Motor City, with its high unemployment, would provide an even better backdrop for criticizing Reagan's economic policies.

But site-selection officials may have been most impressed by San Francisco's admonition that the Democrats had better start making inroads in the West if they hope to win next time. Holding their national convention on the West Coast would be a good start in that direction. Party officials, including national chairman Charles Mannatt of Los Angeles, also believe they would be in a better position to tap the West Coast's vast wealth of contributors by holding the convention there.

Right now, the only real stumbling block to San Francisco's bid is the gnawing concern among party officials that the city's 1,900-member police departmment isn't up to handling security for a major event.

San Franciso may be able to augment its police force and allay those concerns. But as one party official noted last week, at a large reception held by Mayor Marion Barry in the Carnegie Library, "There are probably more (District) police brass in this room than policemen in San Francisco."

It's not surprising if you haven't heard yet that Effi Barry, the mayor's wife, has started a new travel agency. She seems intent on keeping E & E Associates Ltd. under wraps for a while--perhaps until she and a partner can quietly build a clientele through word-of-mouth.

Last week, Barry politely declined to discuss her new venture with a reporter, explaining through the mayor's press secretary that she considers E & E a private matter.

All that can be divined at this point--primarily from a brochure being circulated at the District Building--is that E & E is sponsoring a "Memorial Day Splash" package trip to Jamaica May 27 through June 1.

Barry is a former management consultant, school teacher, air line stewardess and D.C government environmental health inspector. In May 1979, she was named to the board of directors of Independence Federal Savings and Loan Association--a post she held until early this year.

In June 1981, she began a daily show featuring gospel music and discussion of city issues on radio station WYCB. She gave up the program two months ago to launch her travel agency venture.

The mayor said last week his wife decided to open the agency after ruling out several other job opportunities that she was worried might be construed as a potential conflict of interest for her husband.