I think too expensive for one way ticket,by the way,if you need to tranfer in SF,you still a USA visa (tranfer
C1 visa is ok) I think at least you may get a parole come back to USA on border chcekpoint for you go back
to China to apply a new visa,you don't need to buy so high price ticket via Mexico City to China,just via Los
Angeles to China is enough ( if you don't get a visa in Mexico)