It depends on the venue. Most every restaurant in Road Town strictly enforces the rules. Although no one enforces the rules in 'other' public places - such as on the streets.

The further you get into the hills or the 'country' the less the rules are enforced. And in some places restaurants provide separate areas and ash trays.

As far as pot, it's readily available, just as it is in the States. Just ask a trusted local. DO NOT travel to pick it up. Have it delivered. However, you're playing with fire, being a foreigner in a country with strict drug laws.

And there seems to be a particular sense of righteous glee when a foreigner is caught with drugs...even though the BVI's local drug problem is significant.

DO NOT enter the BVI with any illegal drugs. That would be just a silly way to wreck your vacation.