Juan Carlos Torres left Cuba 17 months ago and now works in a Miami bank as a "coffee teller," serving the tiny cups of sweet black coffee the bank's Cuban customers drink in endless quantities.

He speaks no English and says he knows very little about U.S. politics, but there is one political issue about which he has very strong opions. Poundling the table with a vehemence that makes his neat rows of coffee cups jump out of line, Torres says:

"The Panama Canal must remain in the hands of the United States today, tomorrow and for all time. To give the canal to Panama would be to give it to Fidel Castro and to make the Caribbean a Red Communist sea."

On the other side of the Florida peninsula, Howard L. Clarke sits in the tiny living room of his condominium townhouse on the outskirts of St. Petersburg. Surrounding him are the Panamanian artifacts he has collected for 50 years - first as a boy born and raised in the Canal Zone and then as a man who worked on the canal for 37 years.

"What do I think of the Panama Canal treaties? I think they stink," he says. "My whole life has been tied to the canal. To me, it's like giving away my home and my heritage."

More than 400 miles to the north, at a gas station on the road between Pensacola and Panama City, the owner, James Phipps, takes a swallow from a bottle of Dr. Pepper and, in the soft cracker accents of the Florida panhandle, says:

"Like most folks around here, I been a down-the-line Democrat all my life. But I'm with Ronald Reagan on this one. We built the canal. We put billions in it. Why should we give it away just because some dictator says he'll make trouble for us if we don't?" Answers Are the Same

The answers are the same wherever one goes in this vast state. Talks with scores of people in every corner of Florida leave no doubt that public opinion here is overwhelmingly opposed to President Carter's treaties that would turn eventual control of the Panama Canal over to Panama.

That's so much the case that, in the opinion of local political leaders, a referendum on the treaties conducted among Florida's 8.4 million inhabitants probably would produce a thumbs-down vote of between 70 and 80 percent.

Yet, these same politicians agree, Florida also provides a case study of why the treaties, which are about to undergo the cross-fire of Senate debate, now seem likely to win the minimum 67 votes - two-thirds of the Senate - required for their approval. Apparent Contradictions

On their face, these two conclusions seem totally contradictory. But, when one probes beneath the surface, it is possible to see how the workings of the American political system will enable the Carter administration, which has staked so much prestige on the treaties, to get them past the hurdle of Senate approval despite, rather than because of public opinion.

Judging by the example of Florida, the administration's struggle to swing voter sentiment behind the treaties through a massive public education campaign has been an almost unrelieved failure.

Administration strategists decided early that Florida, with its many diverse political constituencies was a microcosm not only of the South - the region where the canal treaties arouse the greatest passions - but, in many respects, of the entire country. High-priority Target

Accordingly, Florida was one of the highest priority targets in the administration's campagign to sell the treaties by dispatching speakers on barn-storming tours through the state and inviting prominent local figures to the White House for pep rallies on the treaties' merits.

In the end, though, people here seemed less impressed by the administration's arguments than by the efforts of the conservative, antitreaty forces who blanketed the state with TV documentaries, newspaper ads and massive direct-mail campaigns. Attitude of Indifference

The result has been a hardening of antitreaty sentiment in all parts of Florida: in the scrub pine north with its Deep South attitudes and allegiances in the go-go central region where the plastic spires of Disney World soar out of a landscape of citrus groves and space-technology industries, in the retirement communities clinging like barnacles to the beaches along the Atlantic and Gulf coasts, in the "Little Havana" neighborhoods of Cuban exiles mushrooming through the Miami area.

Of all the state's major political constiutencies, there is only one - the sizable Jewish community around Miami - where the canal doesn't seem to be an emotional issue. There, the attitude is one of indifference rather than of support for the administration.

In this election year of 1978, all this means the treaties are going to figure rather prominently in the campaign rhetoric heard around Florida. As Bill Taylor, the conservative and savvy Republican state chairman points out:

"We've got a governor's race, races for state offices, for Congress and for the state legislature. In every one of them, you're going to find a lot of candidates - especially on the Republican side - spending a lot of time shaking their fists against the 'giveaway' of the canal."

"Given the sentiment here, it's a great issue for Republicans," he adds. "The treaties are identified with a Democratic president! If I were running for office and my opponent was stuck with a procanal treaty president, I'd wrap it around his neck." Bottom Line: 2 Senators

"But," Taylor concludes, "you've also got to remember that the governor of Florida and all of these other guys don't have diddly squat to do with whether these treaties pass or fail. There's only two people from Florida involved in that - our two senators - and neither of them is up for re-election this year."

In that observation lies the key to why the treaties now seem assured of squeaking through the Senate! Florida's two Democratic senators - Lawton Chiles and Richard Stone - are quite aware of the sentiment in the state; and if either had to go to the hustings this year, they probably would find it impossible to vote for the treaties and get re-elected.

However, there won't be a Senate election here until 1980, when Stone's mandate comes up for renewal. By that time, as Taylor concedes "the canal is going to be a moot issue. People will be worrying about other things, and no one is going to remember or care how he voted on the canal." Pressure Is Off

In short, for Stone and Chiles, the pressure is off. While both have been very careful to keep themselves in the uncommitted column, almost every politician in Florida seems convinced that, once the shouting and arm-flailing of the Senate debate is ended, Chiles and Stones will be among those casting an "aye" vote for the treaties.

Fred Schultz, a former leader of the state legislature and a Democratic Party power, says: "I haven't talked with Lawton or Dick about their views on the canal; but I know both men quite well, and there's no question of where their instincts would lead them.

"Both are party loyalists and have had good relations with Carter. Both have an internaionalist point of view and undoubtedly believe that transferring control of the canal would be good for our foreign relations! It's obvious that they would want to vote for the treaties and have been trying to find a route that will let them do so safely." Burning Issue in South

What he says about the two Florida senators also applies to many of the Senate's other undecided members, particularly those from southern states with internal political situations resembling that of Florida.

From its inception, the canal debate has burned most fiercely in the South, where military bases and American Legion halls abound, where a neocolonialist pride in America's global leadership role is strong and where there is a heavey dollars-and-cents interest in Gulf Coast shipping that makes heavy use of the canal.

And, head counters on both sides agree, the votes of the South's sentators will decide the fate of the treaties. That's because so many of them are still unknown factors in the arithmetic of the impending Senate vote.

Within the Senate, there are approximately 25 hard-core treaty opponents. On the other side, roughly 60 to 65 senators, whether offically declared or not, are generally counted as safe bets to side with the administration. Two Factors at Work

That leaves approximately 10 senators in the unpredictable column. Most are from the South, and the administration hopes enough of them can be lured into the protreaty camp to produce an affirmative vote of 70 or better.

That the administration now seems likely to see its hopes fulfilled is a combination of two factors. One has been the eleventh-hour willingness of Panama's military dictator, Gen. Omar Torrijos, to agree to additions to the treaties spelling out future U.S. rights to intervene militarily against threats to the canal and to priority passage for U.S. warships in time of emergency.

The other is the fact that many of the undecided southern senators are in the same position as Chiles and Stone: they don't face a re-election race this year.

Some Democrats who do - like Georgia's Sam Nunn and Louisiana's J. Bennett Johnston - must contend with the antitreaty attitudes of their constituents and are likely to find the pressures so intense that they will vote no.

But, the others seem to be seizing on the maneuvering room afforded by their freedom from an immediate election contest and the concessions made by Torrijos to move in slow, carefully calculated stages toward a protreaty stance. 'The Baker Ploy'

Among southern politicians, that's become known as "the Baker ploy," after Senate Minority Leader Howard Baker (R-Tenn.). It was Baker who earlier this month visited Panama and convinced Torrijos to make the concessions that will allow him to support the treaties while simultaneously taking credit with his Yennessee constituents for "improving" the treaties to better safeguard U.S. interests.

Florida's Stone has played on that theme even longer and harder than Baker! As a member of the Senate Foreign Relations Committee, Stone has been hammering for weeks at the alleged weaknesses in the treaty deal - the question of U.S. intervention and priority-pasage rights, the rights and obligations of the United States if a new sea-level canal is built in Panama, the properiety of dealing with a Panamanian regime accused of abusing human rights. 'Retreat' Is Attacked

In fact, Stone raised so many objections that, throughout the canal debates, the antitreaty forces were predicting that he would join their side! As recently as Friday, his public rhetoric seemed to support that view.

During a Foreign Relations Committee markup session on the treaties, Stone attacked "treat in our hemisphere" and said he would vote against the treaties unless Carter promised to maintain U.S. military bases in the Caribbean.

Almost on cue, the President responded with a message addressed to Stone assuring him that Washington will "oppose any efforts, direct or indirect, by the Soviet Union to establish military bases" in the hemisphere" and will "maintain our bases in the Caribbean necessary to the defense of the Panama Canal and the security of the United States . . ."

As a result, the committee session ended with Stone taking credit for having clarified U.S. policy on "an important security consideration" and announcing he now probably will vote for the treaties.

Seen through Washington eyes, it looked like politcal granstanding of the most shameless sort. But politicians her in Florida view the matter differently. A loyalist Watchbird

When the shouting is over, they note, Stone will have shown himself to be an administration loyalist. But he also will be able to tell the voters in Florida how his vigilance had helped force Torrijos and Carter into the changes and clarifications that turned the canal agreement into a "good deal" for the United States.

Not everyone has played the game like Stone and Baker. For example, Stone's Florida colleague, Chiles, has elected to simply say as little as possible about the canal. But, when the time comes, it seems certain he too will be voting yes.

During recent days, a similar attern has become increasingly evident throughout much of the South.In Texas, Democrat Llyod Bentsen, who has no race this year, has declared for the treaties and Alabama Democrat John Sparkman, who is retiring fromthe Senate, also lined up in the administration camp Friday.

The treaties probably will still use more votes from the South than they'll win. But, the circumstances of of how and when U.S. senators are elected, almost certainly, will allow enough Southern senators to go against the sentiment in their home states and give Carter enough votes to make the Panama Canal treaties a reality.