Augusta, GA would be perfect! We have this very large abandoned shopping mall on the southside of town that would make a perfect set of a day of the dead type movie (remember the original was set in a shopping mall). This mall is very spooky looking, with weeds growing in the parking alot, sign falling apart, very post apocalyptic look. There are also several abandoned textile mills that would be perfect in a zombie movie.
here is a link about the abandoned mall in Augusta.
Regency Mall