A SUMMER VACATION anywhere beyond the Capital Beltway is all a Washingtonian needs to run smack into all the odd perceptions of the District of Columbia that are held by people in the states. To hear it out there, Washington consists of the United States Government and Everybody Who Feeds Off of it. That's never been a fair tag, of course, but today there is new evidence that Greater Washington -- the city and its suburbs -- is becoming "home" for more and more private firms that have found both happiness and business here.

Most businesses don't move into an area for emotional reasons, of course, and the new wave of firms and associations coming to this town is no exeception. Their executives are "checking the stats" on the local area in terms of business results -- and apparently like what they see. This week, in fact, more than 25 top executives from all over the country and Canada have been taking a look around, as guests of the Greater Washington Board of Trade; if their tour is as successful as the last one conducted by the board two years ago, it will result in some new businesses and jobs here.

Ten of the board's guests on the last tour decided either to expand or relocate in the region; and over a period since January 1976, a total of 56 firms and associations have done so, for a total of 74 additional establishments in the area. Officials estimate that this represents 1,000 new jobs, $9.4 million in personal income per year, $4.4 million in retail sales, 21 new retail establishments, 300,000 square feet of office and retail space and a good $5 million in bank deposits.

That is no mere hay. It is an indication that Greater Washington is a marketplace that offers economic growth and stability. It also is a challenge for the people who live here already and their local leaders, if they expect to make the most of it -- because new businesses don't automatically relieve unemployment rolls. The demand for white-collar workers, people with clerical skills -- typing, acounting, secretarial training and other office experience -- may well be answered with workers from other areas unless there are more intense local efforts to emphasize this kind of training.

It can't all be done in summer programs, either; the city government has to get its jobs program organized and functioning usefully on a year-round basis. Its offerings should be meshed, too, with the programs and campaigns conducted in the private sector. Only then will the constructive economic effects, of these welcome business moves be enjoyed to the fullest.