Answer
Spanish is the primary language of the exam. Candidates need to understand the examiner's commands, road signs, and the wording of the theory section without ongoing assistance from an instructor. The possibility of an interpreter or an adapted format cannot be assumed; it should be agreed in advance with the specific intendencia.
To prepare, learn not only general vocabulary but also short commands: stop, turn, change lanes, park, and continue driving. It is useful to take a few lessons with a Spanish-speaking instructor, even if you already have driving experience.
If your Spanish is not yet sufficient, ask the driving school to show you the question format and conduct a practice lesson. Do not expect a friend to be allowed to translate during the exam: unauthorized assistance can lead to the exam being terminated.