Guatemala has made little discernible progress toward a democratic, open system in the past 30 years. Dictators come and dictators go. So the United States will have to withhold its judgment on the nation's new military ruler following the overthrow of President Efrain Rios Montt. Until it becomes clear where Brig. Gen. Oscar Humberto Mejia Victores intends to take the country, the Reagan administration would do well to keep a prudent distance from the new government even while encouraging it to move toward more democratic rule.
General Mejia Victores, for his part, should know that, because of his right-wing credentials, he will have to surmount considerable skepticism to win the good will of the United States Congress and public. Guatemala has had a history of one repressive ruler after another. A speedy return to civilian rule would thus raise hopes that General Mejia Victores at least wants to give the country a fresh start.
That is not entirely impossible. One apparent reason for the ouster of Rios Montt is that he had proclaimed a state of alert, suspended some civil liberties , and was trying to keep himself in power by delaying legislative and presidential elections. The military is said to be concerned about its reputation after years of political repression and economic distress. However, it can be assumed that the army also seeks to preserve the present conservative order and to legitimize its power - a goal which could intensify the leftist insurgency.
The concern of many Guatemalans will be the potential for more violence and terror in a land that has had an abundance of them. Rios Montt did manage to bring the right-wing ''death squads'' under control in the cities. He also reduced high-level corruption and instituted some limited social reforms. But the extreme brutality continued in the countryside where, according to human rights groups, thousands of civilians, especially among the Indian farmers, were killed and entire villages burned in the government campaign against leftist guerrillas. Will General Mejia Victores be an improvement? Or will he take Guatemala back to the days of former President Lucas Garcia, who was responsible for thousands of deaths?
In many ways Rios Montt, a fundamentalist ''born again'' Christian, seemed an anomaly in a predominantly Roman Catholic country. His evangelical preaching and reliance on the advice of fellow fundamentalists disturbed many Guatemalans. No doubt his unpredictability and quixotic style contributed to the growing opposition to him (even though his policies won the approval of the Reagan administration) and facilitated the military coup.
In the end, there is no question what Guatemala desperately needs. It needs a government with social conscience and moral courage, a government willing after so many decades to do something about the impoverishment of more than half the population, descendants of the Mayan Indians. As long as 2 percent of the population controls two-thirds of the farmland, there can be little hope for social justice or economic progress. To blame ''Marxist-Leninists'' for stirring up strife in Guatemala is moral and political cowardice. The onus for lifting the nation out of its chronic turmoil rests with the government.
Will the new military leadership accept that onus and prove itself better than its predecessors? The outside world awaits to see.