Autocomplete - Search Multiple Tables

I’m trying to implement Autocomplete on my site and allow customers to
search for restaurants by name or city all from one search box.

I can’t seem how to get one edit field to interact with Autocomplete
from multiple controllers. I can add the appropriate code into the
controllers to allow access on the page, but how would I modify:

<% text_field_with_auto_complete :restaurant, :name, {}, {method =>
:get} %>

To allow it to also pull from :city, :name to display mixed results in
the list for the customer to select?

Thanks in advance.