Prince Charles and Diana, Princess of Wales, won't be able to make it to Maryland's 350th birthday party next year. But there's still hope for a touch of royalty, perhaps Prince Andrew.

Gov. Harry Hughes received a polite "no" yesterday from the prince and princess of Wales through the British Embassy in Washington.

"Their royal highnesses have decided that after their major programme of visits to Australia, New Zealand and Canada this year, they want to spend more time at home in 1984," wrote D.M.D. Thomas, charge d'affaires of the British Embassy, in declining the governor's invitation for June 23 of next year.

But Thomas suggested he could approach another member of the family" about a possible visit.

Orwin C. Talbott, chairman of the Maryland Heritage Committee that is planning the festivities, said he probably would take Thomas up on the offer.

In May 1981, Prince Charles visited Virginia to be made a permanent fellow of The College of William and Mary in Williamsburg. But first he came to Maryland--Andrews Air Force Base to be specific. In fact, then-U.S. Chief of Protocol Lenore Annenberg caused quite a stir by curtsying as Prince Charles emerged from his plane.

But the state's turndown might have something to do with the fact that the celebration is two days after young Prince William's birthday--on June 21--and some Britishers didn't take to kindly to his parents' being in Canada this year on the wee prince's first birthday.