hiding normalization with views

I have dealt with postgresql for the last couple of years
with a very simple database, but now I'm trying to do something
a bit more complicated and am having some trouble. Here's a situation:

I am wanting to manage a (postal) mailing list. Nearly everyone
lives in the same few cities, so to store things efficiently (and
minimize typos, etc) I have a few tables:

          Table "customers"
     Column     |  Type   | Modifiers
----------------+---------+-----------
 customer_id    | integer |
 creation_date  | date    |
 name           | text    | not null
 bill_address   | text    |
 bill_city      | integer |
 bill_state     | integer |
 bill_zip       | integer |
 alt_address    | text    |
 alt_city       | integer |
 alt_state      | integer |
 alt_zip        | integer |
 phone          | text    |
 alt_phone      | text    |
 contact_name   | text    |
Unique keys: customers_customer_id_key

        Table "cities"
 Column |  Type   | Modifiers
--------+---------+-----------
 id     | integer |
 city   | text    |

and also "states" and "zips" that look just like "cities".
The problem is, whenever someone looks at or updates the data, I
want "customers.billing_city" and "cities.id" to be hidden and
automatically created when needed. I can create a view
that shows only the data I want, but that doesn't help for INSERTs
and UPDATEs.

Can anyone point me in the right direction or give an example?