Would hardwood or carpet be better for a humid place?
Carpet will be cheaper to have installed, but the life time is much shorter than hardwood.

Look into strand bamboo. I believe it is much harder than any other hardwood and not as susceptible to humidity. I used it in my house on the most of the main level (about 1,500 square feet) and have been very happy with it.

Because it so hard, it is more difficult to install, so you may pay a little more for installation.

I don't know if you can ever avoid all creaks, but most can be avoided by putting down rosin paper first and nailing into the floor joists as much as possible.

UPDATE 1

I'm talking specifically about strand bamboo. Regular bamboo is much softer and scratches a lot easier.