I went a couple of years ago with Virgin Airlines and based myself in Havana.
I thoroughly enjoyed myself, loved talking to and meeting locals, who were very kind and interested in me and where I was from.
I did notice that it was fairly difficult to get round the island. Not many people hired cars. Local/ public transport is very limited and hard for locals so there are not many opportunities for foreigners. Having said that, most of the big 'foreign' hotels have day trips out to the countryside.
I'd get along to your local library and dig out both the Rough Guides and Lonely planet and take it from there.
But whatever you do, you'll have an amazing time.