sale_data_partner/views/sale_view.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
    <data>

      <record id="view_sale_orderfiltercity_view" model="ir.ui.view">
            <field name="name">sale.order.filtercity.views</field>
            <field name="model">sale.order</field>
            <field name="inherit_id" ref="sale.view_order_form" />
            <field name="arch" type="xml">
               <xpath expr="//field[@name='partner_id']" position="after">
                   <field name="city" string="Ciudad"/>
               </xpath>
            </field>
        </record>

        <record id="sale_order_tree" model="ir.ui.view">
            <field name="name">sale_order_tree</field>
            <field name="model">sale.order</field>
            <field name="inherit_id" ref="sale.view_order_tree"/>
            <field name="arch" type="xml">
                <field name="partner_id" position="after">
                    <field name="city"></field>
                </field>
            </field>
         </record>


      <record id="view_sale_orderfiltercity_search" model="ir.ui.view">
            <field name="name">sale.order.filtercity.search1</field>
            <field name="model">sale.order</field>
            <field name="inherit_id" ref="sale.view_sales_order_filter" />
            <field name="arch" type="xml">
              <search>
                  <separator/>
                  <group string="">
                      <filter string="Por Ciudad" context="{'group_by':'city'}"/>
                  </group>
               </search>
            </field>
        </record>

    </data>
</openerp>