No, it is not possible to go from China.

First of all, it would be too far away to go from China. Since I'm in America already, I want to do it this time. Second, it is impossible to get a visa to go to that South American country while you are in China, as I've heard.

So my second question is, if I quit my job, go there, and come back to the States to pack, can I get in again? Note that by then my visa is still valid (within 3 months), but I will have quit my job already.