Too many things to go through here:
the sooner the better, that money is as good as lost. Is anyone actually delusional enough to think America is going to pay back that debt other than through inflation?
It's not just Wen, everyone in the Chinese gov't should be feeling buyer's remorse right now. You think they don't know what's going to happen when Obama administration is adding $2 trillion debt every year? And then add to that, you got the PPIP, the TARP and of course bailing out bankrupt states like California and New Jersey is also on the horizon. The more money China thinks into US treasury, the deeper hole they get into.
let's see, buying gold, silver, oil, any kind of natural resource. in terms of currencies, the euro is safer although not safe by any stretch. NZD and AUD are probably on a better track than most currencies right now. This has nothing to do with South Sea. If you borrowed $2000 to a druggie (in this case US gov't), would you not be concerned about it.
Btw, China right now has Robert Mundell, aka "the father of euro", as an adviser for its economic policy. I don't think we are too far away from a floating currency and eventually challenging USD as the dominant currency. After all, it's already started those currency swaps with different countries. Although at the current time, that's still very insignificant, because CNY is not floating.
As for China buying US treasuries, what they are probably doing is trading some of the longer term treasuries to stuff on the short end.