A small locally owned operator based on the coast road at El Tunco, running day trips to most of what the country offers from a beach base: the Santa Ana crater, the waterfalls in the coffee hills, Suchitoto, the Ruta de las Flores. Guides are bilingual and pickup from where you are staying is included, which matters here because the trailheads are awkward without a car.
They also run the San Salvador airport transfer, which is the other thing everyone arriving at El Tunco needs.