"When we encounter the subversives," said the commander of the little government garrison in this battered village 30 miles southeast of San Salvador, "we shoot. They shoot. We both fall back. We don't want to waste our men."

The region around San Vicente is not exactly guerrilla country, but it's not exactly government country. Like much of the rest of El Salvador, the towns now belong to the Army and National Guard while the insurgents roam virutally freely through the fields.

There are basically two kinds of fighting going on in the countryside. One is the war of major confrontations like tbe fight that has seesawed around Suchitoto north of the capital for the last two months. The Army has now moved into Suchitoto forcefully, while much of the small population has scattered.

The other sort of fighting is the low but steady level of harassment and attrition found here.

The all-our war is mostly limited to a few of the more remote and economically less productive regions such as northern Chalatenango and Morazan, where the guerrillas are entrenched and fighting to create "liberated zones."

To stop them, the government deploys thousands of its troops, with backup from jets and helicopters. Since U.S. equipment is pouring in and advisers are coming with it to organize a quick-reaction battalion -- and the guerrilas are regrouping and attempting to rearm -- that sort of conflict can be expected to grow.

But at the moment this other side of the war, the sort around Tecoluca, is much more widespread. It surfaces at almost any time, almost anywhere in the country.

How much is has affected the economy is difficult to say because there are no statistics to show how many people simply turn their back at barricades or fail to report burnings. But the insecurity caused by the violence is the factor most responsible for the grave state of the economy, according to government officials.

In areas like this, the government troops are hard pressed even to defend themselves, much less the trucks and cart that still somehow persist in plying the roads.

During the January offensive, the guerrillas tried to take this town. The walls of the mayor's office and several homes are still pocked with heavy-caliber bullet holes. But after two days, the guerrillas failed to defeat the garrison and simply disappeared from the streets.

Now they remain in evidence mainly through harassment.

Yesterday morning, a train full of coffee was blown up a few miles to the north. According to the commander here, the guerrillas derailed the engine with small bombs, chased the crew away, then dynamited every car on the track. Damage reportedly exceeded $600,000. Nobody was killed because killing was not the objective. The target is now the economy.

It was the second train blown up at that particular place in the last month. There was no one to guard it from such an attack.

Meanwhile, on a 15-mile stretch of road between here and the departmental capital of San Vicente there are at least eight barricades. Wherever houses on each side of the road give the guerrillas a chance to set up a crossfire they dig a trench through the highway or build barriers of rubble and logs.

Trucks attempting to take sugar cane to a refinery on the highway are turned back or their cargos burned. The Army comes out periodically to patch the asphalt or shove aside the barriers, but the barricades are back within a few days.Sometimes soldiers and guerrillas die in this frustrating process, but most often, "We shoot. They shoot . . ."

A captain in the military headquarters of San Vicente would not say how many troops are in the department, but he insisted that "there are too few."

"There are places we have to leave completely abandoned," said the captain, who like most Salvadoran officers refused to let his name be used.

"The subversives are always moving. It's impossible to give security even on the highway. It's impossible to protect the power lines. We can't guarantee anything. We set up roadblocks and they just move around us."

Government soldiers are spread thin and have to depend on ill-armed, ill-trained paramilitary squads to help patrol even the towns.

There are about 20 regular soldiers of the Army and National Guard here in Tecoluca, and about a dozen members of what is now called the "civilian patrol." These latter seem almost unaware that the name of their organization has been changed and they readily say they are members of "Orden," the notorious paramilitary network norminally disbanded after the 1979 coup.

The "Orden" men are older, leather-faced peasants who carry recently issued but ancient Mauser rifles. The soldiers are mostly in their teens, but carry sophisticated arms. Most have the standard West German G3 rifle. One proudly showed off a new American grenade launcher that came as part of the U.S. arms shipments renewed in January.

Few of these men wear uniforms. Most are dressed in jeans and t-shirts. "When you wear green," said one young recruit from beneath his staw hat, "they can see you from a long way off."

To be readily identifiable as a solider in one of these little towns where the streets run straight to the fields is a risk that few are willing to take anymore.