When Should Course Of Provera Be Started To Delay Periods?

Hi I will be taking a vacation next mont march 11th, thats the week that i will be getting my menstrual cycle , i was told by taking provera 10 mg i can stop the cycle , i was told to take one daily from now feb 20th until the time i come back from vacation so i wont have a period, I just want to know if i should take it as an now or wait afew days before my trip ,i have regular cycles and the last one was the week of feb the 6th, also i was wondering if this medication , if i take it for a month or so will make me gain weight, thanks for your time.