Dan, the USVI are a relatively safe destination. The most populous island of St Thomas has the most crime, and the capital is the centre of most of that, but it's no worse than any other destination, and apart from the usual petty crime, tourists are not targeted. Be careful where you go at night, don't go down alleyways, keep your flashy jewellery locked up at the hotel, show resect and travel in a group. If you wander into a neighbourhood that feels run-down and poor, turn around and leave. Some great restaurants are in slightly seedy areas, so take a taxi at night.
St John and St Croix islands are much more laid back.
Cars drive on the left (even though most are imported left hand drive!). Drivers will veer suddenly to avoid potholes, so watch out for on-coming traffic. Some of the mountain roads are tricky to negotiate.
Mostly the water is safe to drink, but they rely on tank water in rural areas, so take bottled water.
Typhoid can be an issue in rural areas (or if you're going to eat 'local') so get a shot before you arrive.
Phil at the safety hub over 7 years ago