Best time to travel

Hi,
I have paid a deposit on a trip in a ship carring 108 passengers than leaves on March 1 2006. I've heard that March is a really bad time to go, that there is little wildlife around and the landscape is at is worst. Should I forget the deposit and try and get on a smaller boat in January? I decided on March as I want to be in the Amazon for my birthday in April and I don't have that many vacation days or unlimited spending money. However, it was pointed out to me that the trip to Antarctica is a once in a lifetime trip (well for most people!)
Is there anyone out there that has been in March? or been a few times at different times, and can help me?

cheers,

Toni