So funny - just today I realized ALL of my cellulite is gone, and I'm only on day 8!! So, yes, it will work for you in 10 days. Note that your body creates cellulite to store toxins away from your major organs, so if you eat a lot of toxic food or start smoking and/or drinking like a fish, it will come back!
Regarding the pill - there is no reason this should affect that. Often when cleansing and using fiber supplements or binding supplements (ie Bentonite clay) it will drag out medication before it has a chance to work, but The Master Cleanse should be safe.
And regarding the bathroom - ABSOLUTELY you will be going to the bathroom a lot - and you will NOT just be peeing!! What comes out is not always pleasant so you MUST have a bathroom nearby most of the time and note that you may not want anyone to be in there with you! :)
I've done this for 40 days before and am going for 33 this time around, so any more questions - just ask!