Need help with a search logic problem

I'm of course a Ruby noob, but not only that I'm a programing noob, so
I think I would have this problem no matter what language I'm working
with. I'm trying to do a search for my website and can do listings of
properties no problem but I'm having a huge problem when trying to do
a search. I've been reading RailsSpace by Hartl and Prochazka which
is a great book and has gotten me a long way in learning Ruby and
programing but here is my problem. I am trying to use a default
search for ALL cities that match the criteria. When it defaults to a
city or someone chooses a city the search works fine, but it's the ALL
cities options that is giving me fits. Here is the code I'm working
with. Any help would be greatly appreciated:

Property Model: