I am a U.S.?
Im no expert at all. Im in no way a lawyer, and Im also not an American. But my understanding is that it would practically be possible, but technically would still be illegal. The US law bans Americans from spending any money in Cuba, without permission. This makes it practically impossible to visit, since how can you visit without spending any money there? So as far as I know theres no mention about passports or visas, youre just not allowed to spend any money in Cuba. As far as the USA is concerned, youre an American citizen. In practice, lots of Americans visit Cuba. There are legal ways to do it (expensive,through person to person tours, check out the recent Amateur Traveler episode), or you can do it illegally. Lots of people on the Internet have blogged about doing this and nobodys ever been arrested for it. I understand that the Obama administration is working towards normalising relationships with Cuba and wants to overturn this law but cant because of congress, and so has pretty much got the policy that they wont charge anybody. But Im not a lawyer, and its still illegal and my understanding is that in theory the penalties are quite high. Even with only an American passport, what I hear is that a lot of Americans are flying to Mexico, then flying from there to Cuba. I hear that Cuba will obligingly not stamp your passport if you ask, so that theres no evidence of your visit to Cuba (not until you put the photos up on Facebook ;-) ) I dont know if you could fly from Florida to Cuba. I guess you could, although you might raise some eyebrows back at US customs when you return if it was noted that you presented with a US passport when youd just come off a flight from Cuba (its illegal for you to enter the US on your foreign passport). My guess would be that itd be safer and probably not that much more expensive to fly via Mexico