Yesterday it was Puerto Rico's turn to tout its fashions in Washington. Against a backdrop of palm trees and a beach hut, fashion coordinator Edith Battles, sitting in a rattan peacock chair, introduced the fashions of 10 Purerto Rican designers, modeled to the accompaniment of an Xavier Cugat-style band, to 1,350 quests at the annual Salvation Army luncheon.

While the designers names were totally unfamiliar to the audience - only one, Fernando Pena, sells his styles through stores in the United States - the fashions themselves were not. Most of the designers who convened at the Washington Hilton had passed up the trendy ideas of New York and Paris designers for the more familiar ruffles and tiers, lace trims and sequins.

If the Puerto Rican designers have a favorite colleague to emulate, it is julio, the Spanish-born New York designer whose see-through chiffon tops over narrow pants, showed up in many of the collections.

The audience particularly liked the old-fashioned lice trims and flashy sequin styles, and they oohed and aahed over the fashion tricks: a miniskirt that converted to a sequinned gown; a suit peeled off to display a chemise-style dress, and a demure dress with a collar that came off to reveal bare shoulders.

Virtually all of the style reflected the endless summer of Puerto Rico, emphasizing white or bright colors.

The idea for the show originated in an article sent to Battles by Louise Nagel, former community relations director for the Hospital for Sick Children, who moved to Puerto Rico less than a year ago.

According to Martha Torres, Puerto Rico's tourism coordinator for groups and conventions, the Salvation Army provided a vehicle for the promotion of tourism as well as fashion. Sixty musicians and dancers presented a musical revue during the luncheon, followed by the fashion show in which 10 Puerto Rican models were joined by Washington models.

Next week it is Ireland's turn, with a two-week promotion of Irish fashions and crafts at Garfinckel's, in cooperation with the Irish Export Board.