CUERNAVACA, April 30-From the vantage point of the Americans who gather daily for coffee and gossip at the Vienna and its two sister cafes lining Avenida Guerrero opposite the town square, little has happened to distinguish the last few months in Mexico from any others. "Coronel" Sanlers has made his debut treating Cuernavaca to Real Kentucky Fried Chicken at his new concession snuggled between Burger Boy and the snappy Cafe Universal, the weather has grown hotter and the Easter Weck crowds have come and gone. None of these things are surprising. American cultural expansion, hot weather and the passing of vacations does little to differentiate this year from last for the people who sit at the Vienna. But those who cross the street to buy a newspaper at one of the stands in the square can scarcely help realizing that something is up beyond spring. The Mexican government "is sitting on top of a political volcano," one American student with a tendency towards hyperbole says. It is difficult to judge if he is exaggerating.

The incident which has received the most attention was the arrest of twenty allegedly North Korean trained Mexican revolutionaries for plotting the government's overthrow. The uncovering of this group, which calls itself the Movimiento de Accion Revolucienaria and was supposedly aided by the Soviet Union, has given President Luis Echeverria's administration excuse to expel five too-ranking Russian diplomats and begin what some say is a new wave of political repression. In a Nixonian gesture, Echeverria appealed for national unity in the face of crisis while his Partido Revolucionaria Institutional (PRI) bought pages of advertisements in the country's major newspapers to print some of the thousands of telegrams of support sent the president by Mexican leaders. In conjunction with administration flag-waving, there have been stepped up military operations across the country. Along the well-travelled Cuernavaca-Mexico City Highway soldiers march with fixed bayonets. Armed searches at the toll stations have been frequent. Full dress military patrols roam the countryside in the state of Guerrero, famous as the home of Acapulco, while it remains under semi-martial law.

A recent series of gun battles between police and guerrilla-banditos has exacerbated the tension in Guerrero, which has traditionally been Mexico's most warlike and trouble-some section. In March a former state governor and PRI chief was assassinated there by left-wing terrorists. On April 22 a group calling itself the "Comite Armado de Liberacion Emiliano Zapata" announced that if a Guerrero coffee millionaire did not pay 350,000 pesos ransom, his son would be executed. With the demand the group cited the names of six campesinos for whose murder the millionaire is allegedly responsible. On April 27 government agents arrested six suspects in the plot. Guerrero's governor and three top officials were killed in a helicopter crash on April 19 that also might have been caused by guerrilla sabotage.

Last last November there were three head-on freight train collisions that are believed to have been arranged by saboteurs as is the December bombing of a railroad roundhouse in Mexico City in which seven engines were destroyed. But the government has not let the Left take the lead in terrorism. In the State of Sinoloa in North Mexico 13 persons, including three women and a child, were killed when soldiers fired into a fiesta crowd celebrating a baptism. The government explained this, as it has similar incidents, as an attempt to stop narcotics traffic.

THE RECENT conflicts between the government and the Left occur against the background of the massive demonstrations in Mexico City preceding the 1968 Olympics and the massacre that ended them. At one time, an estimated half-million persons were in the city's streets demonstrating against the government. On October 2 troops under the command of then Minister of the Interior Echeverria suddenly opened fire on demonstrators, killing more than 500 in what had the appearance of a highly organized ambush. After the "2 de Octubre Massacre" virtually all open Mexican radical activity ceased. From it, Echeverria gained his reputation as a master of political repression.

But Echeverria's role in Mexican politics is complex. On social and economic issues he is reputed to be a leftist. Echeverria is opposed to the sacrificing of agrarian interests to the program of rapid industrialization that has been government policy. Although it is still too early to see if his administration will be able to fulfill its promises. Echeverria has pledged to have legislation enacted that would substantially help Mexican factory workers and campesinos. There is every indication that he is sincere in this and will be successful. PRI, the party that selected him to be president, is nearly without opposition in its control of the nation's politics.

PRI's influence is omnipresent, and as if to remind everyone of it the party has sprayed the countryside with its name and Echeverria's to an extent that Coke and Pepsi couldn't hope to match. For PRI, Echeverria just represents the next few years. The party has certainly chosen his successor already, and probably his successor's successor. The presidential term is six years long and PRI is wise in its choices. But it does not have a reputation for love of democracy. When in 1965 party chief Carlos Madrazo proposed a system for gubernatorial primaries in Mexican states he was ousted and several years later killed in a plane crash of mysterious origins. Mexican philosopher Octavio Paz compared PRI to the ancient Aztecs. Both, he said, controlled the whole country from the Valley of Mexico (where Mexico City is today), and both have used violence liberally to maintain their power.

Whether PRI will continue to run the country without opposition will be decided by the determination of young Mexicans to force reform. Those who see Mexico now as a political volcano expect students to do the erupting. The only guerrilla group that has acted openly in the last month is the "Cemite Armado de Liberacion Emiliano Zapata" led by veteran revolutionary Genaro Vasquez. Among the groups outside of Guerrero it is difficult to say which are guerrillas and which are banditos. Mexico's healthy but deeply submerged communist party does not have the strength to be a threat to the government. Any change in the situation will have to come from the young people who have been active since 1968.

THOSE people who think that Mexico is teetering on the edge of revolution-and some like to compare the current atmosphere here to that preceding the Mexican Revolution in 1910-must suffer from the wildest delusions. If anything Mexico today is comparable to the United States before the First World War. Ripp'es from the counter culture barely touch the shore. Most Mexican students seem most interested-and not unsurprisingly-in getting themselves into a lucrative profession. The ones involved in the arts hope to find financially rewarding ways to use their abilities. A talented young photographer, rather than wanting to do free-lance work, is studying business administration and hopes to go into advertising. There is no stigma against materialism and few seem seriously interested in politics. Very little is revolutionary about them. With the political complacency of young Mexicans, a mildly popular new president, and an economy that has Mexico at its most prosperous ever, the prophets of Apocalypse are difficult to believe.

In the quiet and heat of mid-afternoon the sound of the Token's ancient hit "The Lion Sleeps Tonight" drifts to the Vienna from radios in the square. Strangely, the song is a colossal hit here and stations often play it a few times an hour. Many would like to believe that in the jungle and the village the revolution is sleeping too. It is more likely that it simply does not exist.