Clouds flecked the clear November sky like wisps of cotton candy and a band played "The Stars and Stripes Forever" as bouquets of brightly colored balloons and the aroma of South Carolina barbecue mingled languidly in the air. With that bit of fanfare and the cutting of a 65-pound cake, the Pennsylvania Avenue Development Corporation's Western Plaza was officially opened yesterday in downtown Washington.

PADC executive director W. Anderson Barnes said the opening of the plaza, a landscaped marble and granite square on Pennsylvania Avenue between 13th and 14th streets NW, marks the first step in the realization of the PADC plan to revamp much of the nation's main street between the White House and the Capitol.

Presiding over the immense cake (yellow with chocolate frosting and a replica of the plaza on top) like a proud father at a christening, Barnes noted that the redevelopment of the avenue is now one-third complete. In the time remaining before the Jan. 20 inaugural, two additional parks will be completed along with the rest of the sidewalks between 13th and 15th streets, he said.

"We will be in good shape in time for the (inaugural) parade," Barnes said.

In a round of speeches before the festivities began, city administrator Elijah B. Rogers called the PADC a "unique combination of the efforts of private enterprise and government," and said the revitalization efforts would lead to the "rebirth of the entire downtown area," increase tourism, and add to the city's tax base.

A persistent heckler in the crowd greeted Rogers' enthusiasm with comments like "What about jobs, man?" and "You ain't done s--- for your own people." Two police officers quietly but firmly insisted that the heckler leave, but he returned in time to make similar observations during remarks by D.C. City Council Chairman Arrington Dixon, who told the crowd of about 300 that many of the city's top officials, including mayor Marion Barry, were not in attendance because "they are out campaigning for President Carter so that efforts such as this will not be hindered."

Later, as vendors offered a variety of wares and a singer crooned "you always hurt the one you love," Dixon said he believed a change in administrations might "alter the thrust" of PADC efforts. But Barnes disagreed, saying the revitalization effort is a bipartisan commitment which will remain firm regardless of who is in office.

PADC chairman Max N. Berry said that when complete the new Pennsylvania Avenue will "bring housing, tourism, and life after dark back to the heart of the city." Plans call for work along the remaining two-thirds of the avenue to begin in 1981.

PADC is authorized to spend up to $200,000,000 for the construction of commercial, office, and residential properties along the ceremonial avenue.