Parque Central is the ordinary civic centre of La Unión: shade trees, benches, vendors, and the slow rhythm of a hot eastern town. It is not grand, but it is the easiest place to take the temperature of local life before heading to the waterfront.
Come in the early evening when the heat eases and families come out. The streets around the park have simple places to eat, and the waterfront is close enough to combine both in a short walk.