Flying from Montego Bay Jamaica to Cuba is no problem. Don't have your passport stamped.(Cubans understand) It's really that simple.
When Air Jamaica was still flying they had pamphlets for travel to Cuba on the plane. The resorts also offered side trips to Cuba...of course they discouraged Americans, but my friend flew to Cuba (Santiago?). He had a lot of fun.
So, yes you can travel...just don't bring back evidence that you were there. It's really that simple.