Legislation to place 250 retarded and other developmentally disabled adults in community facilities, passed in the waning hours of the General Assembly session last week, represented a special triumph for advocates of the mentally retarded in Maryland.

The measure had appeared to be in jeopardy late in the session, when funds legislation to which it had been linked was defeated.

The 250 persons who will be placed in community group homes and day program activities by August 1983 form a small part of the more than 3,000 mentally retarded persons in the state who are waiting for places. But the legislation is "a very significant first step" in helping retarded adults lead more productive and independent lives, says Madeleine Will of Chevy Chase, co-chairman of the Maryland Association for Retarded Citizens (MARC).

In testifying for the legislation, called the community programming bill, MARC activists emphasized a need to care for retarded persons outside of institutions. They pointed out that the state offers educational and job training programs for retarded children only until they reach age 21. Retarded adults placed in institutions often regress after training programs end, and if they live with their parents they often become withdrawn, forget what they have learned and are more and more dependent on their families, say MARC members.

Suzan Gildenhorn of Montgomery County, a member of MARC's government affairs committee, said, "Not only do these people lose their academic skills, but the social skills they have been taught through the years, such as taking public transportation and handling money. These (skills) are forgotten if they are not used."

The number of group homes where retarded adults can live under limited supervision is woefully inadequate, MARC contends. Montgomery County has only 32 such homes, with more than 100 residents. Three more homes are scheduled to open in the spring.

Throughout the state, 1,300 persons have found placement and 3,075 more are waiting for space in residential group homes. Of the latter number, 1,295 live with their families and 1,780 are in institutions.

Some witnesses told of problems, such as elderly parents who have been waiting years for placement of a retarded adult child in a group home or day program, and persons in institutions who are able to hold jobs but have nowhere else to live.

One such parent is Mary Denny of Silver Spring, who has been waiting 14 years to have her son John, now 35, placed in a group home or daytime activity. He suffered brain damage in an accident when he was 6, has frequent seizures and needs constant supervision.

"I am a very patient person, but I just need to know that he'll have a place if he outlives me," said Denny, who is 75 and has been a widow for seven years.

Joanne Perantoni told legislators of her initial opposition when a group home for retarded adults was opened next door to her home in Rockville. She said that after she came to know the four residents and two counselors, they all became good friends.

"They make me feel so relaxed because they are such loving people," she said, and added, "I've been absolutely ecstatic about the individual growth I've seen (among the residents) during the last three years."

In appealing to the budget-conscious legislators, MARC lobbyists said they tried to demonstrate that the state wastes money if it trains people only until they are 21 and then lets their skills deteriorate. Lobbyists also contended that the state loses potential taxpayers if it does not help retarded adults retain their job skills.

During the last two sessions, several legislators have visited group homes at MARC's urging.

"It was important for the legislators to have a real image of retarded people living in the community," said Will, the mother of a retarded 9-year-old boy. "Some had visited institutions before and had been shocked. They were amazed at the distinction between that kind of living and living in group homes."

Tying the fate of the bill to help the retarded to a funds measure was believed necessary in a year when the General Assembly was besieged by requests for money from groups representing special populations ranging from autistic children to the elderly. In addition, the assembly was unsure just how much federal aid state programs would lose.

Gov. Harry Hughes said he would support the community programming bill, introduced by Del. Lorraine Sheehan (D-Prince George's), if the assembly passed a corporate windfall-profits tax bill. The legislation for the retarded was amended so that the number of programs it proposed would cost $1.4 million, the amount the windfall-profits tax was projected to raise.

But when the Senate budget and tax committee killed the windfall-profits tax, said Sheehan, "I thought our bill would also die."

In the last hours of the legislative session, however, an agreement was reached to pay for the community programming through four other bills that had passed, including one raising the rate of interest charged on delinquent state taxes.

According to Sheehan, who has a 16-year-old retarded son, the strategy of MARC and its supporters worked. In spite of the failure of several revenue bills the group supported, she believes its efforts to publicize the need for more community group homes and day program activities, along with the publicity surrounding the defeat of the windfall-profits tax, spurred legislators to make an extra effort to find other sources of funds.