Usually it is about a 2 or 3 week waiting time before you can get the appointment. I would make it ahead of time! plan for 4-6 weeks ahead. They also randomly "close" weeks at a time (I know of them doing this at least once in the past) for immigration medicals, so maybe calling more in advance would be good just in case. Cuba can be pretty random like that. There is no charge at the time of the medical, but it's included in the PRE. However, as of Jan 13 there will no longer be a PVE/PRE for exiting Cuba, so no one is really sure what will happen from that point on! No one can really believe that they would give up the 550 cuc for every person leaving, so maybe they will start charging the medical upfront? It's really in a state of limbo right now and no one knows.... Where are you from in Canada?