Ubuntu Networking :: Start Wifi At Boot (without Being Logged In)

I use Network Manager applet to connect to my lan (I don't use dhcp however). The problem is that my machine runs several servers (http, ftp, smb, ...) and should be ALWAYS accessible whenever the computer power is ON, even if there is no user logged. Another problem is that the connection is dropped if you logout and then login with a different user who doesn't know wireless settings (eg my mother, sister, brohter...)

So, is there a way to get a wireless connection at boot time? I mean, using Network Manager. Previously I used wicd or cli tools (iwconfig and wpa_supplicant) but then I switched to NM cause it was more ubuntuish. I'd still prefer not to use wicd, but NM really seems not good software to me