It wil give you some result, but its certainly not the optimum choice as the MH emits the wrong spectrum for flower. MH is better if your using only sinlge types of light for vegging then switch to HPS. If you can only afford one light set-up then the majority of reading I have done recommends that you go with HPS for the full term of the grow. This may result in more strecthing during veg but will yield better bud results than MH.

This is different from the position that you can afford multiple light set-ups & will run a balance of blue & red spectrum throughout the grow.