There's no longer any doubt: This summer is going to be a banner season for travel in this country. And the Washington area will be no exception.

So if you plan to visit the beaches, amusement parks, resorts, inns and historic places in nearby states, make certain you have confirmed reservations.

The message about cheaper U.S. gasoline, bargain air fares and a dollar worth more at home than overseas is obviously being heard clearly by Washington-area residents, along with the lingering echoes from violence abroad.

Summer vacations in this country will reach the highest level ever recorded, with a 5 percent increase over last year, according to projections by the U.S. Travel Data Center, a nonprofit research center in Washington. And Travel Industry Indicators, a monthly newsletter that reviews trends in the travel industry, confirms that the climate for domestic tourism has never been better.

Here is a report on current expectations from some of the popular close-in destinations and attractions, based on a spot survey of six states:

VIRGINIA:

Virginia Beach. Inquiries are running 13 percent above the same period last year -- and 1985 ended with a 15 percent increase in tourism spending over 1984. Reports from innkeepers and the business community indicate it will be an excellent year, says Jim Ricketts, tourist development coordinator for the city.

Though most of its visitors come from the East Coast, Virginia Beach has expanded its advertising to include Detroit and Chicago, opened a toll-free phone line for Canada and is sponsoring French-language TV spots in Montreal. About 800 rooms have opened for thisseason.

Shenandoah National Park. Attendance has increased only a few percent so far this year,according to Barry Presgraves, director of operations for ARA Virginia Skyline Co. Inc., the concessionaire handling lodging, food, horseback rides and souvenirs in the park.

With 196,000 acres, "we're not bumper-to-bumper or elbow-to-elbow -- there's a lot of room for everyone," says Presgraves.

Colonial Williamsburg. Advance bookings are good. But much of the hotel business in Williamsburg during July and August comes from "walk-ins," says Albert Louer, director of media relations, so it's "a little difficult to predict precisely what the season will bring." There are more than 10,000 rooms in the Williamsburg area; people will find a place to stay no matter what -- though they may not always be able to book their first choice, says Louer.

Busch Gardens, the Old Country, near Colonial Williamsburg. The 360-acre outdoor entertainment park is anticipating record crowds. It opened full time for the season on May 10, but early attendance figures already indicate an increase over last year.

"The Old Country is the Europe that Washington-area residents can reach without flying," says Ray Verser, director of marketing.

Kings Dominion, 20 miles north of Richmond. "Optimistic would be an understatement," says Serena Barry, public relations manager. Attendance at the 400-acre amusement park is currently 13 percent above last year's figure for the same period.

The Homestead, Hot Springs. Vacationers would be "well advised to make their reservations early," suggests Gordon Rockwell, general manager of the resort located on a 15,000-acre estate. "We expect a very good summer . . . We are only about four hours by car from Washington and the last part of the drive is in the Allegheny Mountains and through the George Washington National Forest -- very scenic." The resort is a recipient of the Mobil five-star award.

Shenandoah Valley. "Everybody's showing a gain over last year," according to Joe Grandstaff, executive director of the Shenandoah Valley Travel Association. The valley covers an area about 200 miles long and an average of 30 miles wide, extending from Harpers Ferry, W. Va., on the north to Roanoke, Va., on the south and from the peak of the Blue Ridge Mountains on the east to the West Virginia line on the west.

"Lodging and camping are looking very positive," with sales of antiques, gifts and crafts rising, says Grandstaff.

WEST VIRGINIA:

The Greenbrier, White Sulphur Springs. "Bookings are excellent -- we're running about 6 percent ahead of the same period a year ago," says Jim Searle, director of marketing and development, adding that it seems many of the travelers who are not going to Europe are looking for this type of resort. Situated on 6,500 acres, The Greenbrier has received both the Mobil five-star award and the AAA five-diamond rating.

Coolfont Resort, Berkeley Springs. "May has been fantastic," says a spokesperson, noting that the busiest season usually is from August through October. The resort sits on 1,200 acres.

MARYLAND:

Ocean City. "The hotels are feeling very confident -- it's going to be a strong season," says Bob Rothermel, executive director of the Ocean City Convention Center.

"We're not saying there won't be space," he added, pointing to the more than 30,000 potential rental units: apartments, condos, cottages, hotels and motels. There is always availability in a wide range of prices, Rothermel says, "and our Visitor and Information Center will be able to assist people in finding rooms."

Annapolis. The city may be headed for a 25 percent increase in visitors this year, says Tom Roskelly, director of public information and tourism. In a four-hour period on one recent day at the Chamber of Commerce, telephone requests for travel information were received from dozens of callers around the country.

Talbot County. Rooms probably will be available for awhile on weekdays in St. Michaels, Oxford and Easton, according to the Talbot County Chamber of Commerce, which reports "we're terribly busy." Weekends are generally filled through June, and properties on the water are "filling up as the days go by." Accommodations can still be found in motels on Rte. 50 and at other hotels and bed and breakfasts in the area.

Deep Creek Lake-Garrett County. The promotion council of the area reports they are expecting a 17 percent increase over last year.

DELAWARE:

Wilmington. This city is "gearing up for an especially heavy summer," says Dan Bockover, executive director of the Greater Wilmington Area Convention and Visitors Bureau. Winterthur Museum and Gardens, Hagley Museum and historic New Castle are expected to be affected by the additional traffic generated on I-95 because of the Statue of Liberty celebration, he says.

*The bureau has just opened a new Visitor Center in the rest area of I-95, nine miles south of Wilmington between state Routes 273 and 896. "Hot lines" are available for making hotel reservations inside the center, which is open 24 hours a day, seven days a week. It is also staffed seven days a week from 8 a.m. to 8 p.m. to provide additional information on travel plans, sightseeing and shopping.

Rehoboth Beach and Dewey Beach. Both areas are expecting an above-average summer and fall season, says Sandra Ardis, executive director of the Rehoboth Beach-Dewey Beach Chamber of Commerce. Real estate agencies describe their rental business as "up-tempo."

And though area hotels and motels now offer 1,500 rooms, in addition to accommodations available in inns, guest houses, apartments, condos, cottages and bed-and-breakfast homes, Ardis suggests early planning and strongly advises guests to "come with reservations -- it makes the beginning of your vacation so much easier." August always is the busiest month.

Chester and Delaware Counties. These counties include such popular Brandywine Valley attractions as Longwood Gardens, the Brandywine River Museum, and Winterthur. Early reports indicate attendance and occupancy are up, but no figures were available.

PENNSYLVANIA:

Hershey. The Hershey Entertainment & Resort Co. operates five hotels (four in Pennsylvania), two amusement parks (one in the state), six golf courses (five in Hershey, one in the Poconos), Hershey Gardens and other attractions. It is not a subsidiary of the Hershey Foods Corp. or the Hershey Chocolate Co.

The outlook for summer is optimistic. "All our weekends for June at the Hershey Lodge were sold out in May, which was unusual, and advance summer bookings by vacationers are up 33.9 percent at the Hotel Hershey compared with the same period last year," says Rich Roberts, communications director of the company. The Hershey Hotel in Philadelphia reports advance bookings up 31 percent, and at Hershey Pocono Resort near White Haven bookings have increased 10 percent. "We're expecting a banner year," he says.

The Hershey properties are "a drive-in destination and oriented toward families," says Roberts. The company's central reservations department reports that most callers are booking two or three nights, "and that fits the national trend because with two-income families it's more difficult to schedule two- or three-week vacations," Roberts says. "So families schedule shorter but more frequent trips."

Gettysburg. Battlefield visitor totals in April increased 21 percent over the same period last year, with a 17 percent increase for the first five months of 1986. "It's shaping up as a very good summer," says Vicky Foth, program manager of the Gettysburg Travel Council.

"We don't foresee a problem with accommodations," Foth says, except during the usually very busy 4th of July weekend and the June 29 weekend. (The fourth annual Civil War Heritage Days will be held June 28 through July 6, with a battle reenactment on June 29.)

Pennsylvania Dutch country. Last year the number of visitors stopping at the Visitors Bureau in Lancaster was up 19.6 percent -- this year, the figure had increased an additional 8.5 percent by May 1 and later reached 13 percent over the comparable period in '85, according to Harry L. Flick, president of the bureau.

NEW JERSEY:

Cape May. Tourism has increased over the last few years, but last month "we saw more walk-ins than ever before," says Connie Kosten, director of the city's Welcome Center. Requests for information on tours, accommodations and what-to-do were being received in March, indicating "a much earlier interest than last year," she says.