Killarney, carnaval in Salvador is a good call indeed. FYI, there is a pretty serious pirate problem in the Amazon and you'd want to look into this before going. Most of the pirate activity involves raiding transport boats that carry goods (mainly electronics) out of the "zona franca" of Manaus. There have been a number of deaths, Peter Blake's being the most known. It wasn't a "revenge" killing as suggested above. He was just at the wrong place at the wrong time and reacted. There is a French cruising rally that goes into the Amazon and if I'm not mistaken they hire armed police boats for protection. All boats are at some degree of risk in the Amazon. That said, the rest of Brazil doesn't have a pirate problem. While the Amazon is an amazing cruising destination, there are other equally amazing and less-known cruising grounds. Check out the network of inland rivers, islands and mangroves between Paranaguá, PR
and Cananeia, SP. It's one of the richest ecosystems in Brazil and an incredible place to explore if you have shallow draft.