Not sure if this will work on the Backflip since they customized the setup screen for Blur, but you could try what is described in this video:
Basically you tap the four corners of the screen and it will skip the setup taking you to the home screen. I saw this video long after I had set up my device, so I have no idea if it will work, but it is worth a shot. Also, if that doesn't work try pressing the Menu button to see if there is any way to enable WiFi from the configuration screen.
As far as functioning without the sim, it should be able to do that without any problem.