Banks don't 'buy' homes, they foreclose on them. There is a big difference. And, while you may be able to buy a bank owned property in California, the process is not much different than buying a home from anyone else.
What you may want to consider, however, is doing a 'short sale' on your Wisconsin home. Your credit rating will probably take a hit, but I have heard that, if your payments are kept current, you may be able to buy a home right away after selling your current home 'short ' under some very narrow circumstances.
I would recommend strongly that you talk to a realtor who has the SFR designation (certified as a short sale and foreclosure resource), a mortgage specialist, and perhaps even a lawyer.
Best of luck to you!