Elder Chris Merrill (portrayed by Benjamin Farmer (as Ben Farmer)) is from Salt Lake City. Clackamas Falls, Oregon is where he is doing his Missionary work.
It is never mentioned in dialogue where RJ and Chris are performing their mission, although RJ does mention in voiceover that he is a bit disappointed to only be traveling 6 hours from home for the site of his mission duties.
A letter received by RJ from his girlfriend is addressed to him in Clackamas Falls from her in Idaho Falls.
They go to Clackamas Falls, Oregon to do there Missionary work