It must have been at least as exciting as if Herb had made an appearance. While on a drive along the coast Wednesday, former president Richard Nixon, 73, stopped off at a Burger King restaurant in Stafford Township, N.J., for a snack.

"It was a shock to see him," hostess Doreen Johnson, who served Nixon his lunch, said yesterday. "He wore a powder blue suit, and looks better in person than he does on TV."

The former president ordered a hamburger, french fries and a soft drink. He stayed for about an hour, signed autographs, posed for a picture with Johnson and left a note saying, "Best Wishes to Burger King, home of the Whopper. Love, Richard Nixon."

Manager Lisa Krigel said the workers have already had the note framed. Plaudits for the Poet

Chris Llewellyn, a Washington poet, has received the 1986 Walt Whitman Award of the Academy of American Poets for her first book of poems, "Fragments From the Fire." The manuscript was chosen from more than 1,000 entries in a national competition.

The academy has awarded Llewellyn a $1,000 prize and will purchase 2,000 copies of the prize-winning book for distribution among its members. Llewellyn, who has lived in Washington since 1970, studied at George Washington University. End Notes

Malcolm Forbes may float with a fancy crowd, but before the party he gave Wednesday night for the rich and famous on his 151-foot yacht, he was spotted returning from what appeared to be a quick spin in a small dinghy. Jim Hamill, vice commodore of the Capital Yacht Club, said that before his guests arrived, Forbes apparently was given a ride in a rubber raft by a young boy . . .

If you and 25 of your closest friends want a chance to have tea with Sondra Gotlieb, wife of the Canadian ambassador, you can bid for that opportunity tomorrow night at the 15th annual auction benefiting Sidwell Friends School. Those who prefer basketball can bid on the chance to bring four of their closest friends for a three-on-three with Sen. Bill Bradley, former pro player for the Knicks . . .

For the first time, the American Cancer Society, District of Columbia division, will present a benefit concert. The Kennedy Center event will be held May 4, about two weeks before the annual Cancer Ball. Performers include Peter Allen, Sammy Davis Jr., Phyllis Diller, Ben Vereen and Liona Boyd. Actor John Forsythe will emcee . . .

Italian newspapers reported yesterday that Frank Sinatra may sing for Pope John Paul II this July in St. Peter's Square at a concert that would benefit Third World famine victims. The Corriere Della Sera in Milan quoted an unidentified source as saying that "complex negotiations have been going on for months" to arrange a "mega-concert via satellite which could involve other holy places like the Wailing Wall in Jerusalem." Vatican sources said the pope was unaware of the concert, and that if Sinatra wants to sing for him, he will have to request an audience. Sinatra's office did not return phone calls about the report yesterday . . .

Entertainer Pia Zadora says "I don't know anything about baseball," but that hasn't stopped her from wanting to buy a substantial share of the Portland Beavers baseball club. She and her manager, Tino Barzie, intend to buy 20 to 37.5 percent of the minor league team . . .

Jack and Jo Ann Hinckley, parents of John Hinckley Jr., who was committed to St. Elizabeths after being found not guilty by reason of insanity of attempting to assassinate President Reagan in 1981, were honored yesterday for their efforts to educate the public about mental illness. The Hinckleys were awarded the Howard Safar Memorial Award for distinguished service at the ceremony in Las Vegas. . . .

Cyd Charisse, whose legs were insured for $1 million when she was dancing in Hollywood musicals, will play Lady Hadwellin in the musical "Charlie Girl" in June in London's Victoria Palace theater, it was announced yesterday . . .

Prince Andrew left London for the Bahamas yesterday after a delay caused by escaped snakes. British Airways staff members searched the plane before the prince boarded after baggage handlers saw snakes loose in the cargo hold. They tracked down two harmless American corn snakes that escaped while being shipped to Britain on a flight from New York.