2.0 devices are super-easy - from the Palm Developer site:
The activation-bypass tool is not needed for webOS 2.0 devices.
1. Go to the phone app.
2. On a GSM phone, press "#*DEVMODE#", followed by the call button. On a CDMA phone, press "##DEVMODE#". (If the device is GSM, and there is no SIM card, a screen may be displayed instructing you to install one. Just begin typing the "#*" and the phone app will appear.)
3. The Developer Mode scene will be displayed.
4. Select "On". You will be prompted to re-boot the device.