I believe there was mention of the in-game currency using USD to fit the Lake Tahoe setting - however whether this currency is the "accepted" one come game time, who knows.
Some tribes may only accept scavenged drills, for all I know. I also cannot seem to find the post.. I'm guessing it was merged into another but I can't locate it.
As for NPC's - there will be NPC's in the wild (i.e animals, etc) however, there will be *none* to sell, buy, or give quests. (Totems will be used for player made quests)