In light of another California city going bankrupt, it probably makes sense for PR agencies to negotiate deposits and up-front payments from their public agency contracts?
Previously, such a demand would have been rejected by cities, counties, etc. However, if a municipality really wants your services, they will find a way to "retain" you. When I managed a technology team, we demanded from start-ups at least one-half of the monthly amount at the beginning of the month. This same formula could be tolerable for public agencies.
So, I implore all agencies to stick together on this one. When finances improve, we can relax these demands. What we don't need now is for public agencies to find the agency willing to accept shaky terms.