South of La Esperanza , a dirt highway (in good condition only during the January–May dry season) descends an escarpment down into the hotter lowlands near the Salvadoran border. Beginning from around the area of San Marcos de Sierra, on a clear day one can see the volcanoes of San Vicente and San Miguel across the border in El Salvador.
The road continues down into a small valley, in the middle of which is the town of Concepción, and then continues up again briefly. Beyond Concepción, the road forks three ways, the southeasterly road going through Colomancagua, the southern road through Santa Lucía , and the southwesterly road through San Antonio . All eventually go into El Salvador, but the road through Colomancagua is in the best condition.
It first passes through the border crossing of San Fernando, with (at last report) a Honduran border guard who is happy to stamp your passport, but nobody on the Salvadoran side. Continue to the first major Salvadoran town, Perquín, where there is an interesting museum about the civil war.
From Perquín, the road is paved farther into El Salvador, but be aware that you may have to pay a small fine if you leave El Salvador through a different border, because you don’t have an entry stamp. Returning through the same border is no problem.
The travelers who’ve made the trip rate it as well worth it for the adventure of crossing a remote border, with fine views over the countryside.