I can play offline with steam in sp. With other steam games I can play local coop offline. Yes I know there is a work around to be able to play with my kids but I have limited data on my cell and it is somewhat a pain. Was just wondering if the devs were ever planning on adding the option.If there isn't an internet connection to authenticate with Steam, it won't work.
If you have as little as a basic DSL connection, you should be able to do this. Theoretically it could work on dial-up, but that would be pushing things a tad.