BARBARA BUSH, who has taken to the local life of this city with impressive energy and interest, is not known for lending her name to activities without lending in-person help as well--and her sponsorship of one civic event set for today has been no exception. The only difference this time was an unscheduled detour for Mrs. Bush during a recent field trip in her capacity as sponsor of a longtime local tradition: the 32nd YWCA International Fair, a one-day, 30-embassy bazaar-benefit that begins at 11 this morning in the Washington Hilton Hotel.

The hotel is still where it has always been, but not so the downtown local YWCA--a fact that had escaped the navigator of the car taking Mrs. Bush and other fair volunteers to a pre-event visit. She was driven to what longtime Washingtonians remember fondly as "Y" corner at 17th and K Streets NW., where this venerable local institution had been home, cafeteria and chocolate-chip-cookie heaven to men and women of all races well before desegregated facilities were the norm around town. But what Mrs. Bush saw on this corner was a hole in the ground--because the downtown YWCA doesn't live there anymore.

Next Thursday--famous cookies and all--the new YWCA will open at 624 9th St. NW, where Mrs. Bush finally did arrive for a sneak preview and where, with a little luck and a knowledgeable driver, Justice Sandra Day O'Connor will participate in the dedication ceremonies. In the meantime, Mrs. Bush and more than 600 volunteers who have donated their talents to today's benefit are promising a lively international fiesta of foods, crafts and music for all--that is, all who can find their way to the right Hilton.