So I got the ID wrong yesterday. This is yesterday's snake which is actually Arrhyton exiguum, the Antillean Ground Snake.
As you can see both are small, slender, brown snakes with stripes down the side. They are both quite variable colourwise too. The racer seems to have a yellow chin and have various spots and things one can use for ID. As far as I can tell the easiest way to tell the two apart is that the ground snake is friendly and relaxed whereas the racers rear up like a cobra, hiss and strike at you if you get too close. They lead pretty similar lives although the racers get a little bigger and are a little more easy to find. Both are mildly venomous in a way that is not at all threatening to humans (as far as I know, think bee sting, Ok as long as you're not the unlucky person who's allergic).
They're both pretty speedy too - you can see that in a video I shot of the Ground Snake in the hand and upon release the next morning (once we were sure he was definately OK and not catmolested).
Is the video working? if not go here: