Main recommendations
Walk the historic centre first. It gives the town context before you start driving around the north. Add the Church of San Juan Bautista, the streets around León y Castillo, the local market area and a coffee stop.
For a fuller half day, add Casa y Jardín de la Marquesa, the Arehucas rum distillery and Montaña de Arucas. The mountain viewpoint is especially useful at the beginning of a trip because it helps guests understand the shape of the north.