I looked at your p500 file. It looks fine to me, I see nothing obvious wrong with your arrangement. The fact that you can hear traffic on Fire and EMS talkgroups would imply that your configuration for the Palmetto P25 system is correct and functioning. If you hear traffic on the LE talkgroups but the traffic is not legible ever, then that would indicate that the LE talkgroups are encrypted. If that's true, you and everyone else are out of luck for monitoring LE in Beaufort Co.
You could probably confirm this by running a program called Pro96comm - it will decode the data on the PP25 control channel and I believe it will indicate if talkgroups are encrypted - I've never done that but I believe it will work. That will remove all doubt.
Are you able to hear ANY LE traffic in the clear in Beaufort Co. Sheriff's Department, Beaufort PD, Port Royal PD, Bluffton PD?