The Greyhound site http://www.greyhound.com/ is better for this sort of question than this site is, because it gives you the flexibility to specify different departure dates and times; the price is dependent on exactly when you want to go.
For example, when I did a search for San Bernardino, CA to Boise, ID (the closest I could find to Caldwell; if you're familiar with the area you may be able to find a closer stop... another reason for doing the search yourself on the Greyhound site), I got prices ranging from ~ $200 all the way down to ~$90 (depending on how far in advance I booked the tickets and exactly when I wanted to travel) for one-way "Economy" class tickets. For best prices you should plan on booking at least 2-3 weeks in advance, book your ticket online, and have some flexibility in your travel dates.
Black smoke poured into the bus.
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