You might find these wiki links helpful:
SC Interstate Routes - The RadioReference Wiki - this page gives you a list of which counties you will pass through on your trip, and which Palmetto 800 sites you'll want to program.
http://wiki.radioreference.com/index.php/SC_Highway_Patrol/Department_of_Public_Safety_(SC) - this page will list each SCHP Troop by county, which will tell you which SCHP Troop talkgroups to import. You'll pass through counties in Troop 5, Troop 1, Troop 7 and Troop 6.
You can also use a wildcard, assuming you program the approrpriate sites into the system. But you'll hear a lot of additional traffic beyong SCHP - Darlington Co, Dorchester Co, Berkeley Co, Clarendon Co, Orangeburg Co, Jasper Co, other state agencies, etc. If you're only interested in SCHP, it would be best to program their talkgroups. At least that way you get the alpha-tags.
Enjoy your trip.
Brian