Washington — Out on the street, what are Americans thinking about Grenada? ''It's ridiculous!'' says a woman from Lake Forest, Ill. ''What on earth are we doing there? A Russian threat? Baloney. The Cubans have been around for a long time. I don't see us spreading ourselves all over the world.''
Larry Phillips of Franklin County, Ind., sees it differently. ''I have no problem with the invasion. There was an imminent danger there. Grenada is too close to us and we have to stand up. We will be condemned by other nations, but condemnation didn't stop the Russians in Afghanistan.''
At a moment when the high councils of the world are sorting out power and diplomacy, Americans across the nation - feeling sympathy for families struck by tragedy or concern for national and world stability - speak candidly among themselves. Their quiet concerns, or sometimes total disinterest, is part of the large, slightly recorded dimension of times of crisis.
Brief interviews with American tourists waiting to get into the White House on a sunny morning cannot provide firm conclusions about the public reaction. But even a limited sampling of opinion suggests that the events in Lebanon and Grenada are not necessarily a political liability for President Reagan.
''We should be in Grenada and Lebanon,'' Helen Huus of Northwood, Iowa, says emphatically. ''Unless we take care of all the little pieces (areas where the Soviets are aggressive), there'll be bigger ones to take on - like Afghanistan. I support Reagan's policy.''
Robert McNeil of Seattle agrees. ''I'm concerned about the plot of communism, '' he remarks. ''It grows like a cancer and infiltrates everywhere. That bugs me. We have to call a spade a spade, and Reagan had a golden opportunity.
''As for Lebanon,'' he continues, ''the marines are supposed to be there, but they shouldn't be sitting ducks. They ought to put them on ships where they're not subject to terminal attacks.''
His wife interrupts with a different view about Grenada. ''I'm concerned that England and France are not supporting us in Grenada,'' she says.
Possible American violation of international law, in fact, concerned many of those interviewed. ''I'm appalled by the events,'' says Thomas Crow of Rhinelander, Wis., holding his son by the hand. ''I'm surprised the government excuse is that Americans lives were in jeopardy. There's no evidence of that.'' ''We're going in just because we did not like the government there,'' adds Mrs. Crow. ''We have no right to respond militarily.''
''I'm against intervention,'' says a visitor from Simi Valley, Calif., who didn't want to be named. ''I don't believe in going into small countries against the international system. Let them handle their own affairs.''
A worker with the National Park Service, John Terrell, was visibly eager to get his views out. ''The government is supposed to be set up to keep other countries from invading,'' he says. ''You set up rules (among nations) so your privacy isn't invaded. It's as if you didn't want your kids to do something, and then you broke the rule. What are the kids supposed to think?''
Lebanon was also a burning topic with him. ''That's something that (former Prime Minister Menachem) Begin started, and now the US and the French have to end it,'' says Mr. Terrell. ''It's Vietnam all over again. There the French started it and we had to bail them out. Israel should pull out of Lebanon and let them (the Lebanese) elect the government they want. That's the rules.''
Some felt they did not have all the facts and voiced doubt that Reagan had stated them. ''Who knows?'' says one California resident. ''There may be all sorts of undercurrents we know nothing about. And we're not at the point where we believe our government leaders.''
A willingness to help other countries and concern about losing more American lives in Lebanon were among varied themes struck by others.
Eleanor Merritt of New York City: ''If the Grenada (invasion) helps the people there, I'm for it. If we're going in to aid them to establish a government of their own, that's fine.''
Robert Vaughn of Washington: ''We're probably in Grenada because of the length of the runway, not because of the students. Why didn't we come out and say so? But to allow that (Marxist) government to become entrenched would make it more difficult in the future.''
Carmen Fernandez of Tarzana, Calif.: ''It's all scary! I have an 18-year-old son, and if we go to war, he'll go.''
Edward Darveau of Hemingford, Neb.: ''I'm puzzled as to why we're in Lebanon - or anywhere, for that matter. I suppose we can't pull out right off and lose face.''
Peter Marino of New York, a former marine: ''It's OK what we're doing. The US should be in Grenada because we were asked in.''
Lance Maynard of San Raphael, Calif.: ''I hope we can leave both countries soon. It's all the lesser of two evils. We should stabilize things in Lebanon and get out now. Otherwise there will be more attacks.''
A few people seemed indifferent to the overseas incidents or expressed more concern about the economy. What would they say to President Reagan if he happened to saunter by? David Pusateri, a law student from Pittsburgh: ''I'd ask him why he hasn't balanced the budget.''
''I'd ask him how Nancy is,'' replies one man, clearly unwilling to address the subject.