Tacuba is the practical highland base for El Imposible. The town sits north of the park, close enough to the Ruta de las Flores to fold into a western El Salvador itinerary, and it is where many visitors arrange guides or onward transport.
Do not expect a resort town. Tacuba is useful, local, and low-key, with the park as the main reason to overnight. Ask about trail conditions before committing to a route, especially after heavy rain.