Biking on Caribbean islands

I vacation in Tortola quite a bit, and a 3 hour ride would be quite challenging there. Here's a rental place I know of:

https://www.laststopsports.com/index.htm

The only "safe" place to ride would be around the airport on Tortola/Beef Island, which isn't that much space (many many loops to come close to 3 hours) and is a bit away from the entry port (Road Town). The ride between those two spots would be amazing (and challenging), but there is far too much traffic to do it safely.

I'm not sure if the other islands are the same. Running on the other hand is more manageable - I'd recommend running west from port, It opens up and is fairly scenic (and flat) as you run along the sea. You can easily add hills by going inland from there.

Yes, "wrong" side of the road in Tortola as well. Mainly American cars, but also a mix of European cars, so there may be a few with the driver on the other side.

Agree on swimming... absolutely beautiful! Most of the good beaches are on the north side of the island though.

I lived in Bermuda for a few years and if most other Caribbean roads are anything like theirs, I wouldn't attempt running or riding a bike on them unless your goal is to become one with the pavement.  Very narrow roads with lots of larger vehicles (busses, trucks, etc...) that are allowed to cross the centerline - which squooshes traffic on that other side over.  On top of that, most of the roads have a very fine dusting of sand on them at all times that has caused many a two-wheeled vehicle to go down (been there, done that).  So, unless you're going to ride in the center of the lane and keep up with traffic, I'd second the above - do it aboard the cruise ship.

I've been to 3 of those 5 islands - Tortola, St Maarten, and Barbados.  I've run several times on St Maarten, but never biked.  I wouldn't recommend a long run near Philipsburg.  The traffic around town and the cruise ship dock can be very heavy.  If you took a cab up to Oyster Pond near Orient, it's far enough from both Philipsburg and Marigot that there's not as much traffic, plus it also keeps you away from Middle Region where I've always been told by locals there is more crime.

I wouldn't try biking on any of them.  Most of the cruises I've been on do regular spin classes, so if it were me, I'd hit several of them throughout the week and enjoy the islands with the wife.

ETA: One other suggestion - Plan your training schedule so you do a big build into the vacation.  The week of vacation is recovery.  Then, with 3 weeks between the vacation and your HIM, you can plan something like another 15 day build / 5 day taper before the race. 

Just hate to waste a good opportunity to
bike outside as it may be my only chance to get a good outdoor ride before the
race living near Chicago. Plus I love to ride in fun places as it makes the
miles go by as you explore things. I do remember the roads on Tortola our small
and most islands only have the main drag around the outside of the island.

A 3 hour outside ride in febuary in chicago can get chilly

I am pretty sure that I have seen somebody on BT from St. Maarten.

You should try and search for members that are from the Islands and ask them directly !

Have a nice cruise