If you are using NM for wireless under KDE, and have installed the plasma NM applet, and configured NM to autoconnect to a particular SSID, the autoconnect will only happen if the user that configured NM logs into KDE.

If that user logs out and another logs in, the wireless NIC is disconnected and will not connect unless the new user uses the plasma applet to force connect.

If the second user does not force connection, and you CTRL-ALT-Fn to get to a tty console, the wireless is still not connected, so apparently you get no wireless at runlevel 3.

Worse, the xguest ID does not have the authority to connect wireless through NM, so xguest effectively has no network connectivity at all.

This behavior can't be accidental; it has to be intentional.  But it's wrong.  Network access is supposed to occur at the system level on a multiuser system, and NICs shouldn't connect or disconnect based on who logs on when.

If a user who is authorized to configure an interface sets it to autoconnect, then that's what it ought to do when the system comes up, whether that user logs on or not and whether or not anyone happens to be logged into KDE.

Otherwise, system services like ntpd which need the network will either come up and not work or block until a certain user logs in.