How to download a Steam game without DLCs?

Don't know if this is of interest anymore but currently you can go to the properties and under the DLC tab easily uncheck all DLCs you don't want to install.

After that the Installer size changes considerably, so that seems like what you wanted.

I know this is a rather old question, but for anyone still having this issue:

There is the option to choose which DLC content should be downloaded and installed in the steam beta client. Sign up for the beta, switch you client to beta mode and then under the properties of your game, you can install / uninstall each piece of DLC individually.

Someone with a similar problem contacted Steam support and got the following reply:

"Unfortunately we do not have the ability to remove DLCs from games. Once a DLC is purchased, it is automatically added to the game install files. We understand the inconvenience this may cause."

They gave him the option to remove the DLC from his account, but that was about the best they could do.

Unfortunately, because of the way DLC support in Steam is designed, there is (to my knowledge) no way to download a game without the DLC you bought.

This is only possible if Steam actually sees the DLC as a separate game, but in the case of soundtracks et cetera I'm afraid there's no option.