The US$ has already crashed. Commodities are in a bubble.
That doesn't mean that the US$ can't go lower against the other major currencies... nor does it mean commodities cannot go higher... Some things take longer to pan out than we'd like to think, but this has gone on far longer than many though possible... and we have the added impetus of the end of QE2.
I like to buy things after they have been mushed, and I like to short things that have gone ballistic but are currently falling (there is an old saying on Wall Street "buy green, sell red" that my desk partner from my Bear Stearns days reminded me of last week when I complained about losing money shorting something that was still going up... NEVER call a top or a bottom... never grab a falling knife or step in front of a freight train).
We are in the 8th or 9th inning for commodities. Oil might be different (MENA and Saudi Arabia will have their say), as might Ag commodities (it is impossible to call the weather)... but that's my story and I am sticking to it.
Good luck.