Edgar Schultz, truck driver, was standing patiently in front of the cardboard sign that read "Parade Route Starts Here," chewing on a toothpick and waiting for his hometown band from Bowler, Wis., (population 200), to march by yesterday in Washington's annual Cherry Blossom Festival parade.

Schultz and his wife, Mildred, had rolled into town in their trailer-truck a few days earlier, and they were among the first arrivals for the parade, which attracted about 75,000 spectators despite gloomy skies and the threat of rain.

As the Schultzes stood applauding for each of the colorfully uniformed bands, Earline (Frosty) Frost was standing across the street at Seventh and Constitution, shouting, "Look at that, check it out -- perfectly straight."

"I like that," Frost said, as a rifle corps from an Indiana high school, dressed in prim green and white uniforms, strutted past in perfect two-step strides. Frost had come down to the parade with a group of students and parents to cheer the Dunbar High School Band, who played "Ease on Down the Road" as they moved past.

On another corner, vendor Kevin Stoddard could hear the peppy music of the marching bands, but could barely get a glimpse of the parade. He was dishing out a steady stream of hot dogs for the parade-goers.

The parade is one of the final events of the week-long cherry blossom festivities.The grand presentation ball for the crowning of the 1980 cherry blossom queen was to be held last night at the Sheraton-Washington Hotel.

As in years past, the parade brought thousands of out-of-towners to Washington, some from as far as North Dakota and Texas. But among the guests the parade failed to bring out this year were the ones many had come especially to see -- the temperamental pink blossoms.

Experts say Washington's 5,000 cherry trees -- gifts from Japan -- will not reach the peak of their bloom until Easter, which is next Sunday. This makes it the third year in the last seven years that the blossoms have failed to show up for their own festival.

The cool weather Washington experienced in the latter half of this month has delayed the blooms.

"In a way I'm disappointed [about the cherry blossoms]. But it's not enough to dampen the overall spirit of the day," said Betty Fasick, who drove in from Tyrone, Pa., to see the parade.

She stopped in the middle of her conversation to applaud the Allentown, Pa., high school band. "Oh, here we are, here's Pennsylvania," she said. "For a while I thought we were left out."

All of the bands that participated in the parade qualified through stiff competition. "This is our first time out of Minnesota," said John Vukmanich, the tuba player for the Marching Blues Band of the Virginia (Minn.) High School. "We've been practicing in a foot of snow up there."

Vukmanich had been warming up with the rest of the band on the Mall, where Friday's rain had turned the grass into a path of gooey mush. The repertoire for the parade included, "The Pink Panther," "Espana" and the "Minnesota Rouser.'"

"Hey, want to hear me play 'Roll Out the Barrel' on the tuba?" Vukmanich asked a spectator.