The exam is available in English. You would need to make arrangements ahead of time. A good resource is the Departamento General de Tráfico . Check out their website as it is full of information. Unfortunately it is not in English.

You could also try getting in touch with autoescuelas that serve a larger English speaking expat area in the Costa del Sol, Valencia, Malaga, Canary Islands, etc. They might be able to orient you a bit more.