Go Dive! Are you very busy? You might choose among many PADI courses and many very flexible learning options; among them the opportunity to study online.
As a PADI diver you are guaranteed your certification will be reconized worldwide.
The duration of the PADI courses is flexible, since before you'll be granteed your certification you'll need to master all the skills required by the specific course. This means that the time indicated in the details of the courses is the time usually required to complete it.