Search for a hostfamily in California - Concord/SF in Summer 2009

Hi,
we are two Students at the University of the German Armed Forces, and going to do an internship at Acree Technologies in summer 2009. This includes that we will stay in Concord for 10 weeks, arriving on July 13th and leaving on September 16th. We did also all paper work to do this kind of internship, but there is still the problem of housing in Concord or its environment.
We looked up all the rental sites, but found no results for such a short period. So we are searching for a hostfamily, which is interested in German Guests.
We would be pleased about an offer from a host family. We would be very happy, if you have got any advice or solution for the problem. We are 24 and 20 years old. If necessary we would be pleased to send a short vita.
Sincerly
Felix and Stephan