You know, I really hate to be the one that always rain on people's parades....
However, if you buy with the Dollar (which is weak right now) and buy the Yuan, Euro, or even the Franc (which is strong right now), then, in effect, what you've done is selling LOW (Dollar), and buying HIGH (Yuan, Euro, Franc).
When people mention Forex or even currencies. I tell them that I am indeed investing in it right now. I'm holding Dollars.
Because it's weak and I believe that it will rebound in time. One day, when the Dollar is STRONG, THEN, maybe I'll buy some foreign currencies that I think is weak but will rebound in time. Buy LOW, sell HIGH.
Either that or just buy some decent, well-diversified mutual funds. There is nothing wrong in letting arbitrary indices or experienced fund managers to do the investing for you.