It was a grim winter for the polo-playing set of Montgomery County.

Their major playing field in Potomac had been sold to a developer. Their most experienced players were gradually growing too old to play. And the younger generation in horse country seemed more interested in spending Friday night at the shopping mall than on the polo field.

Now, on the verge of another polo season, the players' luck has changed. They were able to lease the Potomac field from its new owner for at least another two years. They also got a new polo master bent on "opening" what was once the preferred sport of millionaires to those who may have seldom gotten close enough to smell a horse.

For the first time in its 25-year history, the Potomac polo field, once the futf solely of a handful of local estate owners, will be the site of a general polo tryout on May 13.

"Everyone is welcome," according to Bob Beer, president of Washington Polo Association, which is now leasing the field at Glen and Travilah roads. Those who don't bring a horse along can rent one for $10, Beer said.

The tryout is a means of showing that women and ethnic minorities will be welcome in his club, Beer said. But it is particularly an attempt, he added, "to overcome the exclusivity" that once surrounded both the sport and the Potomac Polo community.

"What people don't realize is that polo is no longer an artisocratic thing . . . It's become a family activity. I have seven horses. My wife and my two boys do the cleaning and the feeding," said beer, who lives on a six-acre estate in Potomac.

Polo is in a transitional period, said Joe Muldoon, whose Gone Away Farms Polo Club in Poolesville also is a part of Beer's polo association. "It's moved out of Long Island, Meadowbrook . . . the realm of the millionaires," Muldoon said. "It's getting down to the middle (income) level."

By Muldoon's own tally, the polo aspirant needs to have at least two polo ponies, which can be had, he says, for about $1,000 apiece.

Trailers, for transporting the horses to and from matches, run between $1,000 and $2,000. Then add to that $30 for a riding cap, $100 for the boots, and $400 for a saddle.

For those who don't have the sprawling acreage in which to graze the horses, it costs about $15 a month to have someone board and feed them, Muldoon said.

To attract new players, Beer has hired a professional public relations firm to handle the advertising for the polo matches. By the time the playing season starts May 21, the firm will have posted some 150 signs at shopping centers around the metropolitersers that proclaim "Polo in Potomac Is Better Than Ever," and distributed 1,000 bumper stickers saying, "See Exciting Polo? Potomac, Md./Friday 8 p.m./Sunday 3 p.m.

Beer also is offering a special $250 season's playing fee for beginning polo players. Experienced players must pay $650 a season.

Beer's action have won widespread approval among the association's members, although it marks a departure from the way the Potomac polo has been publicized in the past around the Potomac community.

Thomas Dowd, the former head of the Potomac Polo Club, a predecessor of the Washington association, who sold the playing field to a developer last year, depended on word of mouth within the Potomac community to draw new players and spectators for the games.

Over the past few years, polo in the county had taken a turn downhill. Attendance at the Potomac club's dinners and matches had been flagging. The club also stopped holding its traditional cocktail party after the Friday night games.

But recently, the polo community has been heartened by increased use of the polo motif in the advertising campaigns of several companies.

Ami Shinitsky, editor of Polo Magazine, which has headquarters in Gaithersburg noted that a famous perfume company is now promoting a men's cologne that pictures a polo player mounted on a horse on its bottle.

"Would you believe even McDonald's hamburgers, which is about as far away from aristocracy and wealth as you can get, donated a trophy for the U.S. open polo championship last year?" Shinitsky added.