I did my first cleanse last spring for 14-ish days, partly for weight loss. While it's true you shouldn't cleanse JUST for the weight loss, I did it as a spring board for better habits and my weight did stay off.
I'm doing it again now for the same reasons (cause I've been a slug for the past month).
Speaking purely from ignorance, I would encourage you to not be too tied to the numbers on the scale. Those numbers can be exciting for the first few days, but remember to pay attention to how you FEEL, not just the quantative measurements.
Much success to you! Join the party. We'll keep each other going.