Hi - first of all, I take it you're American from your blog. I have to caution you that you can't legally go to Cuba on your sailboat. I'm not saying don't, I'm not saying do, I'm just telling you what is. However, you seem to be an organized sort (and I do like your boat choice, much better boat than the Gemini, which is at best a coastal cruiser), so I expect you'll research this decision too.
The best launching point for Cuba depends on where you're going in Cuba - for Havana, I'd say Key West, or even the Dry Tortugas - gives you a chance to explore them, plus you get the Gulf Stream advantage crossing over. If you're going to Varadero, I'd suggest Key West or Marathon. If you want to do the entire north coast, enter via the Bahamas, at Puerto de Vita, and go west young man! Cuz if you go east, you'll get the crap beat out of you by wind and waves.
I'd be inclined to stay clear of Cuba from mid to late August through to the end of October - prime hurricane season. May to August would be chancy, but probably not too out of line
. November through to December - easy crossing. December through late March - risk of northers. April through July - easy crossing, but winds tend to the SE then, so KW to Havana would be a motor trip.
Nigel Calder suggests a counterclockwise trip around Cuba - I would agree, as the south coast is easier with no current. As for a return to the US - again, that has issues if you're American - people who have done it generally go via the Bahamas and re-enter as far north as possible, Fort Pierce for example. Since the last stamp in your passport is Bahamas, and Cuba doesn't stamp your passport, immigration and customs will think you've returned from the islands.
I'm NOT recommending this, I just happen to know this is how people have made this trip.
One other caution - leave cruising Cuba until you have a considerable amount of cruising experience. It is not for the uninitiated - there is no real maritime infrastructure for cruising boats. If you get into trouble with the boat, you're on your own there. No Boat US, their Coast Guard isn't equipped to rescue recreational boats....even provisioning can be a major challenge, with grocery stores as much as 50 miles away from some places you'll be.