Where to go depends upon whether you will be land-based or boat-based.
I did my PADI certification
with Sail Caribbean
Divers out of Hodge's Creek, doing both my studying and initial dives at Cooper
Island (they also have an office in The Bight on Norman Island). Subsequently I've dived with Dive BVI with success and can also recommend Blue Water
Divers out of Nanny Cay.
I had lots of time when I did this as I was living aboard
my boat, but if you are on a schedule then I'd also recommend doing your certification
elsewhere so that when you are in the BVI you can dive the sites (and sights) instead of having to nurse a hangover while trying to study dive tables.