Havana is good place for having a excellent vacation, however there are a few things you must know.
There are two seasons in Cuba, one is the May to October rain many often and another season is better for visiting the island because is drier and fresher.
There are two currency CUP and CUC foreigner can use both
1 CUC = 1 USD = 24 CUP
It's better have your cash in CUC however there are some business that have the price in CUP.
Where to eat or drink in Havana isn't a problem because there are many restaurants and bars. Also, there are little restaurants that the Cuban people like, these are cheaper but doesn't have the same comfort.
For moving in Havana you can use taxis or locals bus, the locals bus are very cheap but I don't recommend because also it are full, but I met many foreigner that have taked it and they survived.
For visiting the city there are many places, some you can visit it walking, but others you need transport. You can do a Free Tour for knowing the city, it's very economic.
These are my favorites places in Havana!