When travelling to Cuba is it best to exchange USD before you go or when there?
It is better to exchange USD in Cuba, as you may get a better exchange rate. Just Do not accept offers to exchange currency from anyone who approaches you on the street. It is illegal and a common scam practiced due to the dual currency system used in Cuba.
Larger chain hotels are often the most convenient place to make currency exchanges, but you will be able too to exchange money once you have arrived in Cuba either at the airport or at CADECA bureaus
I Hope this is useful for you.
You cannot exchange USD for Cuban CUCs (which is the money tourists must use) anywhere but in Cuba.
Which means you must get some there, but any you don't spend become mere paper if you bring them out of Cuba.
In the airport, skip the line for the Cadeca (money exchange booth) downstairs by going to the one upstairs.
There's a 10% surcharge on US dollars but none on Canadian dollars or Euros. I suggest you shop around for either of those 2 currencies before you head to Cuba. Trust me -- you will have a great time in Cuba.