!VIVA LA FIESTA!

Adams Morgan bursts with the music and cultures of the 17th annual Hispanic Festival this weekend. Starting at 2 Saturday, there'll be free entertainment on three stages along 18th Street NW between Kalorama and Columbia roads with bands playing salsa, merengue and reggae until 7.

The festival expands on Sunday from 10 to 8. A parade, with floats from 21 countries and Peruvian Paso Fino horses, begins at 1 at Columbia and 16th and continues to Kalorama Road. More than 40 bands will perform, and 250 crafters and food vendors will offer everything from handmade jewelry to banana-stuffed empanadas.

Leave the car at home; it's a 15-minute walk from either the Dupont Circle or Woodley Park/Zoo stations on the Red Line. Call 966-5805 for information.

FUN IN THE SUN

Family Fun Day with WBMW-FM and the National Park Service is noon to 6 Saturday at the Washington Monument grounds. At the Sylvan Theater, entertainment includes the R&B of Stratus, New Visions Dance Theater and oldies by Johnny Artist. Over at the children's stage nearby, beside banjo player David Arnold and mime Mark Jaster, there's face painting and free caricatures. And at 2 you can mouth off at a lip-synch contest. Call 485-9666 for information.

THE SCOTS ARE COMING

Celtic lore fills Alexandria at the 14th annual Virginia Scottish Games this Saturday and Sunday. The games, which center on traditional highland athletics, come to a climax with the caber toss -- a 140-pound pole tossed in the air with the hope that it'll flip over and land where it's supposed to. Beside the brawn, the National Scottish Fiddling Championships are both days and a Scottish country dance party is 8 Friday ($10; $2 to watch). The games go on at Episcopal High School, 3901 West Braddock Road; $12 for the weekend, $8 per day (under 15 free with a grown-up). 838-5005.

REST OF THE BEST The Soap Box Derby is this Saturday (honest!) from 9 to 4 at Varnum and Eastern NE. It's free. Call 279-7174 . . . Twelfth Night, performed by Shakespeare on Wheels, is 8 p.m. Friday, Saturday and Sunday at Glen Echo Park. $3. Call 492-6282 . . . The Ocean City Antiques Show is 1 to 9:30 Friday and Saturday and 1 to 6 Sunday at the Ocean City Convention Center on Coastal Highway. $4. Call 301/289-8311.

CHEAP THRILLS Free or almost free concerts this weekend include: the Montgomery College Rockville Brass Band at Friendship Heights Community Center, 4433 South Park Ave. in Chevy Chase at 7 Sunday. 468-4232 . . . Julia and Company at 8:30 Friday and Saturday at Fort Dupont. 485-7723 . . . the kick-off of the nine-day Jazzin' festival with a New Orleans-style jazz parade at 2 Sunday by the Potomac River Jazz Club at Ballston Common in Arlington. 558-2165 . . . the continuing Concerts on the Canal series at 1:30 Sunday with the Anacostia Concert Choir, Soda Bread and the Buck Hill Quartet at the Foundry Mall (30th and Thomas Jefferson NW) in Georgetown. 862-1300.

THE ATHLETIC LIFE

Pros from the past come swinging back at the Prudential-Bache Grand Champions tournament at Rock Creek Tennis Stadium (16th and Kennedy NW) 6 Friday 'till the finals at 7 Monday. Hardly fading participants include defending champion Dick Stockton, U.S. Open champion Stan Smith and D.C.'s own Harold Solomon. There are still plenty of tickets available for the weekend and few for Monday's finals ($7 to $11.50; call PhoneCharge at 432-0200). Call 429-0433 for information.

Also: Before the top stars of tennis (including Ivan Lendl, Jimmy Connors and Boris Becker) tear up the Rock Creek courts the following week, 56 underdogs give it their best shot this weekend in the qualifying rounds of the Sovran Bank/D.C. National Tennis Classic, at 10:30 Saturday and 11 Sunday. Tickets are $8. (They're still available for the finals and early-round matches Monday through August 2 for $7.50 to $23.50; call 432-0200 to charge or 429-0690 for information.)

Meanwhile, the F.C. Washington soccer team (that's F.C. as in Football Club) makes its debut against Canada's national team at 4 Sunday at the George Mason University Stadium in Fairfax. Tickets ($7, under 13 $4) are available at TicketCenter or via PhoneCharge at 432-0200. Call 223-5400 for details.

SPACE ODYSSEY

For National Space Week (and as part of the museum's "Fly-By-Night" family program), the National Air and Space Museum is having a space costume party from 6 to 9 Friday. Grown-ups and kids can dress as astronauts, aliens and so on to hunt for answers on a cosmic fact-finding mission around the museum's exhibitions. It's free. Call 357-2700.

FAST TIMES

The folks at the Bull Run Street Rod Association will rev things up at a Street Run 9 to 6 Saturday and 9 to 4 Sunday at the Prince William County fairgrounds, south of Manassas on Rte. 234. More than 200 modified pre-1948 cars, custom cars and pre-1970 street machines will show themselves and compete in contests that include egg- and volleyball-relay races which you probably have to see to appreciate. Spectating is $3 a day. Call 471-4351 for information.

PEDAL METTLE

The three-member Haro BMX Freestyle bicycle team comes to Virginia Sunday with more tricks packed into its 20-inch bikes than you can shake a sprocket wrench at. Their 45-minute aerial show goes on at the Bicycle Exchange shops at 9514 Main St. in Fairfax (at noon) and at Countryside Shopping Center in Sterling (at 4 p.m.). Free. 323-0500.