My Dad (non US citizen) went a few years ago. He had his mexican counsel with him, so he took care of the details. But $5 will take care of them not stamping your passport.
I here for $20, you get escorted off the plane, into a lounge, given a cigar and a mojito, while some one clears immigration, customs, gets your luggage, puts the luggage in the car, and the gets you when the car is ready to take you to the hotel. I read this on a travel web site on suggestions for Cuba. It is legal and promoted by the government.
Personally, risk versus reward does not seem appealing. Dad was not too impressed and said it was kind of depressing. Plus, the food is not that good. A good meal is only adequate, even in the private restaurants.
If I wanted to go to the Carribean for vacation, I can think of many other islands to visit, rather than Cuba.
I think the US policy is dumb and hypocritical, but I bet in the next 5 years or so, the counrty will open up to Americans. Then you can travel with impunity.
If you really want to go, suggestion above on a charitable trip seems the best bet. At least you will feel good about your trip and help the image of the US abroad.