From a Rasmussen immigration poll from last month (link):

68% of U.S. voters oppose the creation of sanctuary cities. Only 13% favor the creation of cities that give safe haven to illegal immigrants. Nineteen percent (19%) are not sure.

Forty-nine percent (49%) say federal and state government funds should be cut off to cities that provide sanctuary to illegal immigrants. Thirty-three percent (33%) disagree and oppose any funding cutoff. Eighteen percent (18%) aren’t sure.

Fifty percent (50%) of voters say sanctuary policies that protect illegal immigrants lead to an increase in crime. Just 20% do not believe this to be true, while 30% are undecided.