not sure how this changes with 10.04, but in my experince with 8.04- you
will only give yourself a bit of work to do after installation if you are
not connected to the internet. You will have figure out how to manually set
up your /etc/network/interfaces file before you can ever connect to the
internet again and also manually add the default repositories and such to
your sources.list. network manager also may behave oddly.

I don't want extra work, I'd prefer the downloads!

I am running Kubuntu and there was zero downloading during the installation.
Everything is on the installation CD. It does not need an internet
connection until you re-boot and it checks for undates. BTW, the
installation was no longer than an Ubuntu installation. Are you installing
from the alternate CD? That could make a difference.

No alternate. Using the standard i386 32bits CD installation. During the
install, it seems to have two sessions of downloading. I don't remember the
message during the first part, but the second set of downloads had to do with
language packs. I do select USA-Alternative-International when setting up my
keyboard since I'm in Canada/Quebec and need accents (ex: é è ë) when typing in
French. Could that be why the install fetches language packs?

Anyway, the install went well and only Firefox seemed a bit finicky about adding
too many Add-ons at the same time. And I had to let Amarok flag me and download
the restricted stuff since Kpackagekit still passes through but does nothing
when I tried to download the Kubuntu-restricted package.

That could be the case as I have truthfully never downloaded language packs
as my language is Canadian English with a US keyboard. I would not think
that they could be that large, but as I say I have no experience. Learn
something new everyday!

I'm in Canada also, and use the standard US keyboard. When I clicked on
"update the installer" it spent several minutes downloading many things, one
of which was language packs. I didn't pay much attention to the rest but the
installation went smoothly.