$(function() {
    $('#id_project').on('change', function()
    {
    var id_project = $('#id_project').val();
    $.ajax(
    {
        url: "ff.php",
        type: "POST",
        data:{id_project},
        dataType: "html",
        success: function(data)
        {
            var datos = data.nb_informacion_general_localizacion;
            alert(datos);
        },
    })
});
});

$id_project = $_POST['id_project'];
$sql = "bla bla bla";
while ($row = pg_fetch_assoc($result)) {
  echo $row['id_project'];
  echo $row['nb_informacion_general_localizacion'];
}