Could you explain a little bit why my question was so "stupid"?Very simply, when you have installed the very basic debian system, and provided you have a connection to the internet, the system can update itself to whichever flavor of debian you want.
I've already said I have a 56k connection. I don't see why I can't download the cds (or the first DVD) from my office (100K/s) and then install from the Cds. If some packages will need to be updated from the network it won't be such a big problem, but I would like to have the most I can from the Cds. But it looks like only the stable distribution comes with "non_US" and "US" CDs, and my question was "are the testing CDs "US" or "non_US""?