Code:
/run SendChatMessage("Casting "..GetSpellLink("Resurrection").." on "..UnitName("target") or "No Target",GetNumRaidMembers()>0 and "RAID" or GetNumPartyMembers()>0 and "PARTY" or "SAY")
Simply added a GetNumPartyMembers() and make it use "SAY" if you are not in raid nor party.