This may be THE article to passive-aggressively pass on to your vehically-challenged friends.

Here's the entire Idaho Driver's Handbook in PDF, and here's the bit on four way stops, which applies not only to Twin Falls but to all of Idaho, page 2-5:

Yielding to Other Drivers

You must yield to other drivers:

At four-way stops. The first vehicle to arrive at a four-way stop has the right of way. If two vehicles arrive at the same time, the vehicle on the left must yield to the vehicle on the right.