Please note that because of the flight timings, you will have to overnight in MEX on the way to HAV.

But one other thing - zap7 do you already speak some Spanish or are you starting from more or less nothing? The reason I ask is that Cuban Spanish has a pronounced accent and if you learn to speak Spanish like that from the beginning, you will never lose the accent again.

Going to Cuba to learn Spanish is like going to Alabama or Scotland to learn English. Certainly possible, probably a lot of fun, but not really advisable from a linguistic standpoint.

I learned Spanish in Cuernavaca, Mexico (about 90 minutes south of MEX) and can wholeheartedly recommend that. La Antigua, Guatemala is also a very popular and very effective choice for learning Spanish (both the Mexican and the Guatemalan accent are a bit more "neutral" - definitely identifiable as "New World" Spanish, but not as far removed from the Iberian original), and they're also very reasonable in terms of cost. Of course, purists say that there is only one place to learn Spanish, and that place is Salamanca, but it just doesn't begin to compare in terms of cost if you're looking at several weeks or even months of instruction.