>It hangs while looking for adb devices. 

The message you saw right before it hang would be helpful.

>Is there a way to get it to boot without looking for ADB devices (other
>than giving it a serial console. I can't spare the serial port)?

Well, then you wouldn't have a console! (adb device is necessary for the
console device to interact with the keyboard)  If the ADB on your model is
not supported yet, I'm afraid that the serial console is only your option.

ken