The White House with its manicured lawns and tall iron fence couldn't compete as a tourist attraction yesterday with the jumble of garish, billboard-sized protest signs across the street in Lafayette Park.

Busloads of schoolchildren from Hilton Head Island, S.C., and Richmond cautiously inspected the 20 huge protest signs that face the White House and then snapped pictures of the signs, the park's sole protester and of each other posing with the signs. The White House was lucky to get one exposure.

Those photographs of the protest signs that have lined Pennsylvania Avenue since July 1983 may become historic pictures by next month because of new rules issued by the National Park Service.

The new regulations restrict both the size and number of protest signs in the park and ban the plywood structures that some have called an eyesore.

Under the regulations, signs placed in the park must be no larger than four feet in either dimension and no thicker than one-quarter inch. Each protester is limited to two signs.

Concepcion Picciotto, 42, who maintains a round-the-clock vigil in the park against nuclear weapons, has 20 colorful but deteriorating signs and plays hostess to the park visitors.

Picciotto, who sleeps sitting in a chair in order to skirt existing park service regulations, said she is ready to battle the park service over the new regulations that will oust her from her home.

"The new rules are shocking and horrible," said Picciotto. "This is a unique display of democracy here and the people who see this make me compliments. We will go to court to stop them."

The signs, many with water-damaged photographs and artwork, are shabby. Bundles of sodden clothes and paper bags with rotting food are strewn about near some of the signs.

Many who visit the park inspect the signs cautiously and some stop to hear Picciotto explain the vigil that she has maintained since June 1981.

Alec Alexander, 24, who refused to identify the government agency where he works, said, "I admire someone who can stick with a cause but the signs are a disgrace. It looks . . . like a shipwreck . . . . "

A Soviet doctor in town for a medical convention said through a translator that he approved of the signs.

"It is important for people to be able to protest," said Dr. Guennodi Mikhalov. "In the Soviet Union, we have posters protesting nuclear war everywhere. They are on houses and on trees."

Late yesterday afternoon, James Glynn shepherded 170 sixth graders through the park. All were wearing blue and white baseball hats.

While the youngsters shyly snapped pictures of Picciotto and her signs, their chaperon shook his head.

"I think if she hold a sign up, that is fine," he said. "That is a basic right. But I don't think it is appropriate for shanties to be built in the park."