Two years ago, developers of luxury condominium projects in Georgetown were humming with optimism: Overall prospects for sales, coupled with the proposed rebirth of the Georgetown waterfront area, could not have been better. There seemed to be an inexhaustible public appetite for expensive Georgetown condominium apartments.

Today sales of the exposed-brick condominiums with circular stirways, skylights and, in some cases, swimming pools are as slow in Georgetown as in other areas of the city. Agents said they hope interest rates will decline and the Reagan administration will be able to get the economy on the right track so that sales will improve soon.

In addition, some of Georgetown's promising new commercial developments also have remained empty because of the poor economic climate. Georgetown, long a popular shopping district, now has some store windows covered with brown paper bearing brokers' telephone numbers.

As if to add insult to injury, plans for a $154 million residential and commercial development on the waterfront were rejected this month by the federal Fine Arts Commission -- which last spring had given preliminary approval for the project. The city is reviewing building permit applications for the complex of 350 luxury town houses, shops and offices proposed by the Western Development Corp., but the Fine Arts Commission's decision is likely to hold. For the moment, at least, the waterfront will keep its cement plant, trash piles and parking lots.

Only one of Georgetown's five major residential condominium projects -- the Papermill -- has sold out.

The last of the first 101 units completed at the Papermill garden complex in the 1000 block of Papermill Court were sold about two weeks ago, said Jim Saputo, one of the developers. A second group of 87 units at Papermill, in a rehabilitated manufacturing plant, will be on the market within a few months, Saputo said.

"Traffic has been good on the weekends but bad during the week," Saputo said. "We had 12 7/8 financing, and even with that we didn't have an easy time."

Saputo said he is optimistic about sales at the second phase of Papermill, although he has had his doubts -- "certainly . . . in today's real estate market."

The Canal House condominiums in the 3200 block of Grace Street NW, part of an as-yet-unfinished retail and residential complex along M Street NW, has only six of its 35 apartment units remaining. Six have been sold so far this year. Prices range between $150,000 and $185,000, said sales manager Jack Cummings.

Bad weather and poor parking have hurt Canal House sales, Cummings said.But he added that he hopes to sell the remaining units in the next couple of months.

"We've had a very slow time now," said Maxine Calamos, sales manager of Wadsworth House, a 32-unit midrise project in the 1000 block of 31st Street NW, with prices ranging from $99,000 to $399,000. "Everyone's having a slow time around here."

Since last November, nine of the Wadsworth units have been sold. Since the first of the year, one has been sold, Calamos said.

"We were not really ready yet," she said because apartments are in different stages of completion. In addition, "traffic is very slow, the weather's been bad. It should start picking up," she said.

Contrary to some beliefs, even the rich sometimes put off purchases during hard economic times, said Chuck Martin, sales manager at the James Place high-rise project in the 1000 block of 30th Street NW. Many prospective owners at James Place consider their home there as a "Washington pad" or second home, he said. First-time home buyers and renters are the ones "itching for their own place," Martin said. James Place purchasers "don't need to move," he said, so they may defer purchases until the economy improves.

James Place apartments sell between $155,600 and $287,700, Martin said. The penthouse already has been sold for $369,500. So far, 23 of the 77 units in the complex have been sold since it opened last September.

"Georgetown has been slow compared to Dupont Circle and other less expensive places for two years," Martin said. "The reason for that is prices."

At the Flour Mill, 16 of the development's 55 units remain unsold, said Martha Clark, a sales agent. Prices there range from $108,000 to $545,000. But Clark said she doesn't think she'll have a hard time selling the remaining units, "especially with all the Republicans."