At every atm you can get cash with a visa card issued by a non-us bank. Changing cash at a CadeCa can be a little annoying (waiting, passport). The reception at Habana Libre is changing cash without passport and no waiting but the rate is 5 to 10 % less.
Casa particulares and paladares (private restaurants) do not accept credit cards.
US $ are not the best cash, bring euros or can $.