Retail buyers, who this week completed a month-long marathon of fashion shows in Paris, London, Milan and New York, would have done well to stop by Washington this weekend before hanging up their order pads. They would have discovered several of the 11 local designers whose clothes were shown at the Renwick Gallery on Saturday to be well worth their attention and encouragement -- as well as their dollars.

Washington Fashion Group, an international organization of more than 6,000 women in the fashion business, sponsored, with G Street Fabrics, two shows in the newly restored Grand Salon of the Renwick. They were both to benefit the upcoming retrospective show "The Woven and Graphic Art of Anni Albers," which opens in that museum next June.

"President Reagan has asked us to seek outside support whenever possible for the arts," said Barbara Nosanow, assistant director for museum programs at the National Museum of American Arts, of which the Renwick Gallery is a department.

The focus on Anni Albers, the 85-year-old textile artist and widow of abstract painter Josef Albers, worked well for the designers whose strength is more often textile weave and color rather than design. In fact, it is when these designers get tricky with cut and fit that most of them are in over their heads.

But not all. Lisa Mandle of Baltimore, whose clothes opened the show, handles fabric mixes in a loose, easy way that is theatrical at times, but often very wearable. While some of the things looked very much at home in the sumptuous Victorian salon of the Renwick, others would be right in place on the streets of London today, Georgetown tomorrow. Mandle started "playing with fabrics as a child," she said as slides were shown of her at work. "And I'm still playing."

Elvenyia Barton plays with a wide range of fibers, furs and even beads in her sweater collages, done deftly to render each element to its best advantage. "I try not to disturb the natural property of the fiber," she said. She uses her mixes well, sticking to soft, appropriate natural colors or soft hues for men and women.

Joan Konkel has given herself an interesting challenge, integrating her metal sculptures into clothing, an idea few established designers would dare tackle. And she makes it work particularly well on the collars that can be used in different costumes and when she incorporates her metalwork into the design of necklines and waistlines.

Jewelry designer Joke van Ommen gave herself a special assignment for the Fashion Group show, creating the kind of contemporary jewelry she believes in and making it visible to a large audience from a small runway. "I don't make little sculptures with pins at the back," she said. "I want my jewelry to be worn in many ways, so the wearer is involved in the creative process."

Van Ommen, whose gallery on Pennsylvania Avenue carries the designs of many others as well as her own jewelry, effectively accomplished what she set out to do. With models dressed in diving suits so as not to detract from the forms, she used circles of synthetic materials as necklaces, as well as for ornaments for the head and the body.

Designers were selected for the Fashion Group show from about 150 who submitted sketches or photographs of their work. According to Lani Barovick-Brown, regional director of Washington Fashion Group, about 35 designers were called back to show the selection committee actual examples before the final 11 were selected.

Before each person's clothes were modeled Saturday, a slide presentation showing the designer's creative process was projected on a screen to one side of the round platforms that made up the runway.

The slides showed Cynthia Boyer, for example, in the basement of her Cleveland Park home preparing the wool felt that she uses most effectively in white-background short jackets and vests.

As with any designers, even the heavy hitters who have been showing their collections recently, some styles work more effectively than others. Teri Potter Phillips succeeds when she sticks to her simplest shapes and trips a bit when panels and ribbons start flying. Katherine Koumouseas' strong suit was her finale, feather sleeves on dinner suits and feather coats that should have a big following.

Cuban-born Regino Collazo, who now lives in Adelphi, and whose clothes were shown last, is probably the most skilled designer of the lot. He used bright colors wisely tamed with black and a deep sapphire blue with white for clothes that were pretty and quite dramatic. He said he likes the 1960s and uses details that make some of the clothes look a bit retro. But the audience loved it and isn't that really what counts?