Welcome mats are out in the city, the suburbs and the country. On Capitol Hill, the 22nd annual home tour is Sunday, 1 to 6. Visit 10 homes for $10, payable Sunday at the starting point, Eastern Market, Seventh and North Carolina SE. (Call 544-6048.) In Bethesda and Potomac, "Homes of merit" will be toured on Sunday, 1:30 to 5:30. The homes are notable for art collections, architecture, interior design or landscaping. Tickets are $8.50. (Call 656-3430.) In Poolesville, St. Peter's Church is offering its 19th - country homes tour Saturday, 10 to 5. It's $5. (Call 301/972-8460.)

As historic preservation week winds down, the Citizens' Committee to Save Historic Rhodes Tavern will be out in force Saturday from 10 to dusk. They're holding a paint - in on 15th Street NW, opposite the 'Treasury Building, to focus on that block's edifices. Bring art supplies. (Call 857-7287.) And then there's the Association for the Preservation of the 1700 Block of N Street NW. It's holding a concert in the Gralyn Garden, 1745N, on Sunday at 4. It's $5 and the raindate is May 20. CAPTION: Picture, no caption