I went to Cuba last year (not with JY). We went in April; like you, I don't like it too hot also I wanted to avoid the hurricane season which starts late June. It was still pretty hot in April, particularly on the south coast of the island (Trinidad do Cuba and Cienfuegos). No bug problems in April. If you have any other general questions please ask but as I say it was not a JY holiday so I can't comment on that side of things.

RM