Is El Salvador governed by bullets, or a congress?

A Western diplomat calls it ''the freest, best-attended elections in this country's history.'' A left-wing intellectual calls it ''another devaluation of the democratic process.''

On the surface, they are talking about the year-old Salvadorean election of March 28, 1982, which put 60 people into the newly formed Constituent Assembly.

Underneath, however, they are pondering a far deeper question: Has this war-torn nation made any significant progress away from its oligarchy and toward democracy over the past year - and has the electoral process, urged so strongly by the United States, helped?

To some, the operations of the Constituent Assembly show that words, rather than bullets, are beginning to govern the nation.

Many here point proudly to the fact that members of the assembly now seem to limit their violence against one another to name-calling - although there is still extreme violence in this country. Last year the US State Department reports an average of 219 civilians were killed each month in political violence , although it notes that is a significant decrease from the average of 445 per month in 1981. (Many sources say these figures are too low.)

''The people in the assembly are behaving like (US) congressmen,'' says a Western diplomat in a bit of backhanded praise. Because no party has a majority, he explains more seriously, ''the assembly has to make deals - and that is something that is absolutely new in this country.''

''Now they believe in the political process,'' adds President Alvaro Magana with obvious satisfaction.

The past year, according to close observers, has seen several important developments:

* The assembly is wrapping up work on its new 240-article constitution, which should be in draft form by the end of this month.

* Attempts by rightists in the assembly to gut the nation's land-reform program were rebuffed last spring - with subsequent eroding of the power of the assembly's elected leader, right-wing former Maj. Roberto d'Aubuisson.

* Leaders of the major parties, under the coaxing of President Magana, signed the Pact of Apeneca in August. The pact set forth seven key objectives (peace, democratization, human rights, economic recovery, social and economic reforms, confidence and security, and a strengthening of international support), and established a Peace Commission, a Human Rights Commission, and a Political Commission. The Political Commission, the President syas, is a group of party leaders which ''gives support to my decisions.'' It has already met some 40 times, he adds, with ''an attitude of cooperation that is incredible.''

Other observers, however, are less enthusiastic. ''The fact that the system has increased its tolerance for name-calling is not necessarily a demonstration that democratic institutions are fortified,'' says one left-wing intellectual.

He also notes that, although the 1979 coup was unique in the depth of reforms it attempted, the process of coup-to-constitution-to-presidential-election is ''a recurrent cycle in Salvadorean history.''

A senior Salvadorean bureaucrat, asked to assess the man-in-the-street mood, says that ''from March (1982) on, the average man feels there has been no progress.''

And one Salvadorean economist who follows national affairs closely says that ''there have been minor, secondary advances during the last two years,'' but adds that ''the net result has been a deterioration and a complication of the national problems.''

As a way to resolve those ''national problems,'' the US has been urging Dr. Magana's government toward speedy, broad, and free elections. The country was hardly back from its week-long Easter holiday, in fact, when President Magana got a phone call from President Reagan on that subject. Though no date has been set, Dr. Magana now foresees elections sometime in December.

But the deeper issue troubling many Salvadoreans is the relevance of the electoral process - and the extent to which its results will be honored. Many here are asking:

* How broadly based was the 1982 election? The official Salvadorean view, attested to by some 300 foreign observers, is that the elections were fair - anddespite threats by guerrillas to disrupt the process, some 1.5 million people (85 percent of eligible Salvadoreans) turned out.

But some political scientists here say those figures may be grossly inflated - that such tallies do not square with the numbers of people lining up at polling booths and the speed at which the lines moved. They say the number of voters may have been more like 800,000 - still impressive.

* Who won the election?

Even those most skeptical of the total figures acknowledge that the percentage of the vote received by the leading parties was approximately correct - 40 percent to the left-of-center Christian Democratic Party of former President Jose Napoleon Duarte, and 29 percent to the right-wing Nationalist Republican Alliance (ARENA) of Major d'Aubuisson. The problem: No single party won, requiring that a coalition government be formed.

* Did those who were elected form the government?Shortly after the election, ARENA and four other smaller parties, whose combined votes totaled 60 percent of the field, declared that they had formed a coalition. But their leader (Major d'Aubuisson) and their far-right platform proved unacceptable to the US Congress , according to Western diplomats here.

So in a whirwind visit in April 1982 by House Majority Leader James Wright (D) of Texas, House Foreign Affairs Committee chairman Clement J. Zablocki, Gen. Vernon Walters, former deputy director of the CIA and now a top State Department trouble-shooter, a compromise was hammered out. Result: Dr. Magana, an independent, was picked as president, and Major d'Aubuisson became president of the Constituent Assembly.

While many here do not object to the end result, they question the means to that end - which they see as clear evidence of US manipulation of Salvadorean affairs.

Because of this US influence, one academician predicts, ''regardless of who the voters choose (in the next election), the Christian Democrats are going to be the winners.''

But US Ambassador Deane R. Hinton objects to the notion that he ''runs'' El Salvador. ''I've got a lot of influence,'' he says, ''but I don't run it.

''If I were running this place,'' he adds, ''a lot of things would be different.''