On the ILS CONTROL PANEL (on the AFT AISLE STAND), change the ILS frequency to a frequency not used at that airport. i.e. if I land at MEL (YMML) ILS16, I just change the ILS frequency from 109.70 to 110.70, and the ILS no longer appears on the PFD.
Note. I did this after I had already turned the AP OFF (using the big DISENGAGE button on the MCP), and both FD switches OFF, so I'm not sure if you can do it before then..