ITS STILL FAR too early to know if some travel agents and wholesalers are overestimating the number of curious Americans who now may be eager to spend between $400-$575 each for a week's vacation in Cuba.

It is not too early to strongly deplore a bombing and threats of violence against those who would provide air and ship transportation to Castro's island - even for a traveler like myself who has no desire to return to Havana on a pleasure trip before full diplomatic relations and regular scheduled air service have been restored between Cuba and this country.

Since I resent any governmental attempt (other than during a state of war or national emergency) to limit the freedom of its citizens to travel, I am naturally outraged by attempts of terrorists living in this country to intimidate Americans and tell them where they cannot go. There have been at least two recent incidents:

Mackey International Airlines, which had announced it would begin a series of charter flights to Cuba from Florida, canceled its plans last month after its Fort Lauderdale office was bombed.

Carras Cruise Lines canceled three cruises of the Daphne from New Orleans to Havana scheduled for this month and put the vessel into Mediteranean service after receiving bomb threats. One cruise was completed. (See related story on Page G8.) Officials have indicated they still plan to resume Cuba cruises in January. Other cruise lines are tempted but wary.

"In traveling to Cuba, we are not making a sympathetic political statement," travel wholesaler John Keller, president of Caribbean Holidays, Inc., emphasized last week. "We are merely exercising our right to travel."

It is no secret, of course, that a small corps of militant anti-Castroites, originally trained by the CIA for clandestine operations against Cuba in the '60s, lives in Miami among the thousands of Cubans who form the huge, volatile exile community. That community is also strongly anti-Castro and anti-Communist. Buffeted by a bewildering series of political events and setbacks in their effort (once approved by Washington) to destroy Castro and bring down his government, often with attacks launched form bases in this country; and feeling victimized by "broken promises" from the U.S. government dating from the Bay of Pigs invasion, the voluble militants are often associated with terrorist activities.

It is also no secret that Fidel Castro badly needs U.S. dollars to bolster his sagging economy and continue his revolution. The price of sugar, his major export, has plummeted, and a revival of American tourism to the one-time "Pearl of the Antilles" could bring in millions. Castro himself told his people on the day the Daphne arrived in port, "Better days are coming."

There are indicatios that the Carter administration's tentative steps toward normalizing relations (which included lifting restrictions on American travel to Cuba last March) are not unwelcome to perhaps fhalf of the Cuban exiles, many of whom want to go back to visit their families. The extremists and terrorists, see tourism as a dangerous threat that may speed full diplomatic relations and reduce the economic strain on the Cuban government.

Former Secretary of State Henry Kissinger, in a speech June 5, said the United States should not resume diplomatic relations with Cuba. He charged that Cuba had helped the Soviet Union to increase its influence on the African continent, and warned of the possibility of "problems in the Caribbean area and the Western Hemisphere." Castro, whose government is still propped up financially by the Russians, recently admitted to holding nearly 3,000 political prisoners (the State Department has indicated the figure actually may be between 10,000-15,000) and said he does not believe there will be full normalization of relations with this country until what he refers to as President Carter's "second term."

Though many Americans feel it may be time to wind up the dispute with Castro, many others are confused by the Carter administration's Cuban policy and the unconcerned statements by U.N. Ambassador Young about Cuban military intervention in Africa, and some worry about reports that Castro agents are continuing subversive efforts in Latin America. Most disturbed are the Cuban exiles. But threatening to set off a bomb is hardly the same as, for example, touching off a travel boycott.

While the U.S. State Department (and a shuddering travel industry that is very dollar-conscious) understandably may take a dim view of individual citizens playing international politics, from time to time Americans have withheld their dollars from dollar-hungry foreign governments as a way of personally protesting certain policies of those governments. Results have varied according to the intensity of the "boycott" and how dependent a country is on tourism receipts.

Travel boycotts, though they have not yet actually involved broad organizing and committees, may be merely an individual matter - as in the case of those who will not visit the Soviet Union because of violations of human rights, who cross South Africa off their list because of institutional discrimination against blacks, or who simply refuse to go to any country ruled by a military dictator. A boycott may also begin with mass cancellations of group tours by one packager, as occurred in late 1975 when B'nai B'rith, a Washington-based Jewish service orgainzation, retaliated against certain policies of then-Mexican President Luis Echeverria. The subsequent drop in Jewish and non-Jewish tourism cost that country millions in vital dollar exchange, but Mexico's new president, Jose Lopez Portillo, swiftly took steps to ment the breach.

Those who generally oppose travel boycotts point to the fact that if a traveler starts crossing countries off his or her list because of displeasing internal political factors, there would soon be very few countries left to visit. They also argue that the boycotting tourist thus is denied an opportunity to learn firsthand about current conditions, that the withholding of dollars often hurts the innocent worker more than the government, and that boycotts may invite retaliation in kind. But at least they don't kill people.

What is the latest word for Americans seeking to travel to Cuba?

First, aside from ideological or political considerations, some travel industry officials admit that there are good reasons why many Americans may not find Cuba the right choice today for a vacation. Unless the U.S. tourist has a strong desire to see how the Cuban revolution looks from inside (and, whatever the valid criticism about totalitarian, "Big Brother" methods of a Communist state with unique Latin overtones, the life of the Cuban peasant certainly has been greatly improved), other Caribbean islands offer better value for the vacation dollar.

As syndicated travel writer Horace Sutton put it after a recent trip to havana, "In the socialist world that embraces Cuba, the gambling is gone, the old hotels are out of style, there is very little to buy and blue movies can be seen to home."

If you decided to go, you will almost certainly have to buy a package tour. While eager is to welcome U.S. visitors, Cuba is not now encouraging visits by individuals because it feels it can better handle groups with its limited resources.

Despite all the hoopla, to date few tours specifically aimed at Americans have taken off, and all have involved flying by way Mexico, Jamaica or the main departure point, Canada. The tour packagers or wholesalers have used Cubana, Mexicana or Air Canada. No scheduled U.S. airlines have shown any interest in resuming regular service to Havana.

For some years Unitours, a Canadian tour operator, has offered weekly winter departures from Montreal and Toronto, using Cubana and Air Canada.Canadians have made up more than 50 per cent of Cuba's visitors. Unitours vice president of marketing, George Whitfield, has just "completed discussions in Havana" with Cubatur, the Cuban government tourist agency, and has received a guarantee of "40 hotel rooms a week" in the Cuban capital and more rooms at the beach. With those accomdations, and regular Air Canada flights from New York, Boston, Chicago and Cleveland to Toronto for connection with Cubana, Unitours yesterday began its summer program of 11 one-week trips to Cuba.

Whitfield said his firm can handle about 80 passengers a week. Cost of the tour, which includes roundtrip air fare, a choice of either 3 nights in Havana and 4 at the beach, or 4 nights in Havana, 3 at beach, with all meals, transfers and some entertainment, will be around $550 per person. "It takes a maximum of three weeks to process the papers," Whitfield said. "If demand increases from the United States, we are prepared to extend the program through the fall." If a tourist wants to spend the entire week at the beach, the price will about $400, Whitfield added.

Travel agents Alex Lopez and John Gunter of Global Travel in Arlington, Va., have already arranged for two group tours to Cuba that carried mostly Washington-area residents, Guntner said they are now preparing a special interest tour on Aug. 6, via Montreal and Cubana, for 40 faculty members and students from George Washington University.

Carribean Holidays of New York, which has a "firm commitment from Cubatur" for hotel rooms, according to John Keller, may become the first wholesaler to offer charters to Cuba departing directly from the United States. Keller confirmed last week that each flight could carry 170-180 passengers, and he is now involved in securing the planes. He said he would offer not only the Havana-beach package, but also trips to the interior of Cuba including a visit to the Bay of Pigs. Cost would be between $550-$575, and would be all-inclusive (transportation, all meals, nightly cocktail parties, signtseeing). Names of passengers will be telexed to Havana two weeks prior to departure and approval or disapproval will be telexed back to the tour operator. Americans will need only their passports, Keller said. Tours are scheduled to begin in October.

Referring to the recent threats, Keller said:

"It would strike me as rather strange if the President of the United States would allow Americans to travel to Cuba, and the Treasury Department would make the necessary changes in regulations, and then the law enforcement officers of this country could not protect American citizens. It would be a sad day if terrorists and thugs were allowed to keep people from exercising their legal rights to travel freely . . . "

Orbitair International Ltd. of New York, operating through its subsidiary, Cuban Travel Bureau, Inc., and Treasure Tours of Canada, is now taking about 20 Americans to Cuba each week on an 8-day, $434 beach package from Montreal. The flight also carries Canadians.

Other tour operators have indicated they are planning trips to Cuba. It is wise to consult an experienced travel agent who can vouch for the reliability of the wholesaler/packager. As always, read the fine print.

Rosenberg is Travel Editor of The Washington Post.