Washington area blacks support abortion on demand by a 2-to-1 ratio, and a majority believe that judges should be handing out longer sentences to criminals, according to a recent Washington Post poll.

Despite a perception among social workers and others that low-income blacks have a cultural bias against abortion, that is not borne out by the poll results.

Support for abortion on demand was expressed by a majority of blacks of both sexes, at all income levels, and with all levels of education, though the margin of support was smaller at the lower-income levels and among men.

Overall, 64 percent of blacks polled locally supported legal abortions for any reason, compared with 55 percent of blacks polled nationally. Other public opinion polls have shown that about 40 percent of Americans as a whole approve of abortion on demand.

The District is faced with serious prison crowding, but a majority of black city residents polled want to see criminals get tougher sentences. For the Washington area as a whole, 57 percent of the blacks polled said sentences should be longer, while 5 percent said they should be shorter; in the District alone, the number wanting stronger sentences was 60 percent.

At the same time, 70 percent of area blacks interviewed said they felt "very" or "somewhat" safe when alone at night on streets in their neighborhoods. Seven percent in the area had been the victims of break-ins in the last year, compared with 13 percent nationally, and 7 percent had been robbed in the last year.

The wide-ranging poll found that more than 20 years after passage of national civil rights laws, most Washington area blacks say that blacks here are discriminated against in getting decent housing, getting skilled and managerial jobs and in the wages they are paid.

In the predominantly black District of Columbia, which has its own strong antidiscrimination laws, for example, 62 percent of black residents feel there still is racial discrimination in housing.

The actual experience of those polled locally is not as grim, however, with a substantial majority saying they do not believe that they have been discriminated against in education, housing or employment. At the same time, a significant minority of 41 percent said they have been discriminated against in what they are paid, compared with 57 percent who said they have not been.

The local telephone survey was conducted Jan. 15 to 19 among 619 blacks in the Washington area. The Washington Post and ABC News also surveyed 1,022 blacks nationwide on many of the same issues.

Black Washingtonians are better off than blacks in the United States as a whole in terms of higher incomes, less unemployment and more two-earner families, the poll found.

But the views expressed by blacks locally and nationally are strikingly similar on most of the issues they were questioned about. For example, black Washingtonians' views closely matched those of blacks nationally in these areas:

*66 percent gave President Reagan an unfavorable rating compared to 19 percent giving him a favorable rating.

*89 percent had a favorable opinion of civil rights activist Jesse L. Jackson, while only 5 percent had an unfavorable opinion.

*Nation of Islam Minister Louis Farrakhan, whose opinions -- particularly on Jews -- have stirred controversy, was viewed favorably by only 26 percent and unfavorably by 29 percent, with 45 percent saying they had no opinion.

*69 percent said police in most cities do not treat blacks as fairly as they do whites.

*44 percent said income and living conditions of most blacks are getting worse. But when asked about their own experiences, 31 percent said their income and living conditions are getting better, 21 percent said they are getting worse, and nearly half said their situation is staying the same.

Black feelings about Jews appeared to be ambiguous, with 43 percent locally disagreeing with a statement that "anti-Jewish feeling . . .has been brought on by Jews themselves" and 26 percent agreeing with the statement, but almost a third of those polled said they did not know.

Sixty-one percent of black Washingtonians said they had at least one "fairly close friend" who is white, but the percentage is lower here than in the country as a whole and lower among District residents than those living in the surrounding suburbs.

On their children's friends, 19 percent said all were black, 42 percent said they were mostly black, 34 percent said half were white and half were black.

A majority of those polled had no children under 18 living in their household; however, 37 percent had one or two, 9 percent had three or four, and only 1 percent had more than four.

Black Washingtonians appeared deeply divided over the role of government programs. A plurality of 48 percent said welfare keeps people from improving themselves, but another 39 percent said it helps people until they can stand on their own. They were nearly even, 46 percent to 42 percent, on whether blacks, because of past discrimination, should get financial aid not available to whites in similar circumstances.

But by an overwhelming 70 percent, they believe that blacks are not progressing as fast as they should because whites do not want them to get ahead. Whites have either a "great deal" or a "fair amount" of prejudice against blacks, according to 88 percent of those polled.

At the same time, 59 percent put blacks themselves in those same categories of being prejudiced against other blacks. This was a higher percentage than believed that Jews, Asian Americans and Hispanics were that prejudiced.