So far, I have only been into Marina Hemingway (November 2016 - more info on my blog), but I am presently in Isla Mujeres, Mexico
and headed for the marina on the west end (Los Morros), later this week. Hemmingway had plenty of fuel
. When I was researching things I got a great response from "nolagal" on this forum. You might search for that thread or check his blog - See S/V WAHOO: Six Weeks along the Cuban South Coast
I have heard good reports about the new marina in Veraderro, in terms of good facilities, fuel etc. Also, Wally Moran is doing a live Q and A session on Cuba tomorrow at 6pm I think (June 1). If you search him on Google+ you should find info plus a recording of his last Cuba Q and A session. I think that was about a year ago.
I hope that helps a bit! Good luck!