If you remove the Wifly unit, does the lcd screen work ok with the same code?
edit: I don't think the IRQ is supposed to be an output. I think that is a read line on the Arduino. I removed this part of my response to prevent a possible conflict on the WiFly shield pins.
My recommendation is get the code working with the lcd display, then install the WiFly shield and go from there. Find what is interfering.
It appears from the schematic that the WiFly is powered from Vin, not +5v. Are you providing power to the Arduino using Vin? That is the power jack, not the usb.