jQuery Double Escaping Ampersand

I am trying to figure out how to double escape POSTED form data that is sent to an XML API using ajax. Here is the on form submit ajax function.

$.validator.setDefaults({
    submitHandler: function() {
        var $form = $("#signupForm");
            $.ajax({
             type: "POST",
             url: "http://ift.tt/1LI4Rgi",
             data: $("#signupForm").serialize(),
               success: function() {
                    alert("Copy Completed");
               }
        });

    }
});

The issue that I am having is that when it is processed by the vendor's api the human readable "&" truncates everything after it.

If I manually submit the form using "&", the API inserts the full string into the vendor's database. I need to convert "&" to "&" within all fields in the of the serialized string.

I was looking at this...but not quite sure where it need to be placed in the function above to submit the modify values.

var values = $("#signupForm").serialize();
values = value.replace("&", "&");

Thanks jlimited