A complex area, timewise:

http://OnTimeZone.com/images/caribbean.jpg (includes recent changes in Quinta Roo and the Turks and Caicos.)

(magenta lines = time zone borders)
(blue lines = dst observance borders)

I wonder if the recent thaw in US/Cuban relations will have any tangential change in economic relationship between the Caymans and Cuba. If so it might increase pressure to adopt DST.

Steve Jones
OnTimeZone.com