Why does your friend think there is a higher probability of depreciation in the US$, than in housing? Does he believe housing prices will stay flat?
Why do you have to put your money in US$, when you could buy stocks, euros, Canadian $, yen, gold, oil, precious metals?
I also believe the dollar will depreciate, and would like to diversify, but I don’t know if it will, or by how much. However, housing prices are falling. That is a fact. Your friend seems to be missing something?