Seagrass or Sisal or other inexpensive options

We are soon to be owners of an eichler in Foster City. We've read many recommendations on holding off on making decisions about re-doing anything until living in it for awhile but we do have to replace some carpeting (mostly because it is white and we have a toddler and dog, but its also pretty worn).

We keep thinking we want to do concrete floors or cork in the future but can't afford the expense right now. So our thought is to replace the carpet with Sisal or Sea Grass because of its affordability and the natural aspect for the next few years.

So has anyone else used Sisal or Seagrass with success? And there is a disclaimer about Seagrass regarding humitiy and mold, is this somehting to be concerned about with and Eichler slabs and radiant heat?

Does anyone have any other inexpensive flooring recommendations? (I also lean towards green design so while I like alot of VCT options the off gassing aspect is a deterent for me).

Anyway thanks for any input!
tania