How to pass more than one param to jQuery UI Autocomplete?

How to pass more than one param to jQuery UI Autocomplete?

The developer predicted only one param inside this plugin :(
I need at least two to compose SQL select.

I have something like [test code]:

    $(function() {

            $("#state").autocomplete({

                source: "states.php?city="+param1,
                minLength: 2,                           
                select: function(event, ui) {
                    $('#state_id').val(ui.item.id);
                    $('#abbrev').val(ui.item.abbrev);
                }
            });
        });

Param1 should be value taken from input filed [<input type="text" id="city"  name="city" />].
I cannot make it works. When I define  source: "states.php?city="+$('#city').val(),  city is simply empty in url.
I tried as well     var param1 = $('#state').bind('keyup', function() { $('#city').val() } )  but it shows some strange characters not the value taken form city field....
I do not see anywhere example how to send second param with this plugin...
Anyone has some idea? Thanks.