Like a gentle breeze from the Caribbean, an air of modest optimism wafts over Cancun. As the leaders of 22 nations opened their economic development talks on this resort island, it appeared clear that a consensus on at least limited goals would be reached.
American officials have emphasized repeatedly that the fact that talks among such a diverse group of nations are taking place at all means some kind of ''success.'' But beyond that, it seems that vague but potentially significant suggestions for future economic development will emerge from the Oct. 22-23 meetings.
President Reagan, President Jose Lopez Portillo of Mexico, and a number of other participants, have, meanwhile, set expectations for the summit meetings so low that almost any consensus will have to look like success. For President Lopez Portillo, soon to leave office, the summit conference is a crowning achievement.
Great differences in point of view clearly remain between President Reagan on the one hand and the Mexican President and leaders of other developing countries on the other. There are apparently significant differences between the US and several key allies - France and West Germany, and to a lesser degree Britain as well.
But most of the leaders of the eight industrialized and 14 developing nations gathered here seem to have decided that it is too early in the Reagan administration for them to seek confrontation. Better to coax President Reagan toward their point of view, they seem to say, than to insult him.
On the eve of the talks, Secretary of State Alexander M. Haig Jr. spoke of an ''emerging consensus.'' Mexico's Foreign Minister Jorge Castaneda said there would be agreement on food and energy as well as on a framework for future negotiations. All this is likely to take the form of suggestions rather than any formal agreement.
Presidential spokesman Larry Speakes told reporters that President Reagan was encouraged by the meetings that he held Oct. 21, prior to the formal opening of the summit conference, with leaders from five other nations. The President, Mr. Speakes said, feels he has begun a ''warm relationship'' with several leaders whom he had not met previously and was also pleased by their ''reception'' of his viewpoint.
Aside from such nice words and an emerging limited consensus, however, there has been considerable subtle and not-so-subtle sniping at - if not direct confrontation with - President Reagan:
France's Socialist President Francois Mitterrand, in speeches made in Mexico a few days prior to the Cancun summit, denounced political, economic, and cultural ''imperialism'' - an apparent reference to the United States.
In an interview published on the eve of the summit, President Lopez Portillo took issue with President Reagan's emphasis on private enterprise as the key to economic development in the poor nations. He said he thought events would prove such an emphasis to be wrong.
But President Reagan and other officials had agreed well before the summit that there is a role for government, and not just private enterprise, to play in development.
US officials say that the problem is to get beyond rhetoric to concrete solutions. In their view, up until now, more than two decades of talks on development issues have produced little more than sound and fury.
But three of America's key allies - Britain, France, and West Germany - have endorsed the idea of continuing with so-called global negotiations on development issues at the United Nations. The Reagan administration is reluctant to renew such negotiations, involving more than 100 nations, where the US can easily be outvoted. The US wants to channel Cancun talks into institutions where it holds great influence, such as the World Bank and International Monetary Fund. But the US might be willing to compromise by agreeing to some form of UN talks, particularly within specialized UN agencies.
The Cancun conference opened shortly after 10 a.m. on Oct. 22 with President Reagan not in his chair. The President arrived at 10:13 after President Lopez Portillo had formally opened the meeting. An American Secret Service agent remarked over his radio at one point, ''Everyone is here except Rawhide. They're about to start things without him.'' There was speculation Mr. Reagan was late because he was making changes in his opening statement.