Let me go out on a limb and say that the percentage of Jews on any kind of public assistance is very low. Even though most probably think welfare is good.
You might be surprised at the number of Jews in the United States on public assistance. This is particularly true of the ultra-Orthodox or Hasidic Jews who tend to have large families and are generally not as well educated in secular ways. It also is enhanced by the recession and the relatively easy availability of the government programs.
In general, though, I would presume that the percentage of Jews on public assistance is less than the average for the US as a whole, but I haven't seen any statistics on this.