Seven have been reported on Antigua, all but one badly derelict. However, they were all reported as being Antigua Sugar locomotives, all thought to be 2ft 6in guage. I wonder if the two you saw on the pier were different engines. Did you take a picture of them?
There is still an intact railroad in Trinidad. The Hunslet diesels are stored, two of the original Kitson & Co. steam engines are preserved on the island. The Railway Preservation News website had a brief on this railroad last year.
A french built steam locomotive is on Martinique. A Kerr Stuart & Co. locomotive is reported on St. Kitts. I have three listed for Costa Rica, but I believe there are more.