I think it's okay to do the first month through translation just to give a foundation, especially for "function words", such as the, a, and, if, whether, either, or, neither, nor, because their meanings are abstract so it's obviously easier to teach them through translation. But yeah, once the groundwork is done, instruction in the target language is much better.
For example, if a student asks what the word "lodilla" means, obviously their Spanish is going to benefit more by saying "es en la pared, naranja, rectángulo" while drawing a rectangle shape with your fingers, than by simply saying "it's a brick".