I know this is an old question but for those who was struggling with the same issue:
You need to dig into the Doc's here:
https://github.com/blueimp/jQuery-File-Upload/wiki/Options
And there is a list of helpful events:
$('#fileupload')
.bind('fileuploadadd', function (e, data) {/* ... */})
.bind('fileuploadsubmit', function (e, data) {/* ... */})
.bind('fileuploadsend', function (e, data) {/* ... */})
.bind('fileuploaddone', function (e, data) {/* ... */})
.bind('fileuploadfail', function (e, data) {/* ... */})
.bind('fileuploadalways', function (e, data) {/* ... */})
.bind('fileuploadprogress', function (e, data) {/* ... */})
.bind('fileuploadprogressall', function (e, data) {/* ... */})
.bind('fileuploadstart', function (e) {/* ... */})
.bind('fileuploadstop', function (e) {/* ... */})
.bind('fileuploadchange', function (e, data) {/* ... */})
.bind('fileuploadpaste', function (e, data) {/* ... */})
.bind('fileuploaddrop', function (e, data) {/* ... */})
.bind('fileuploaddragover', function (e) {/* ... */})
.bind('fileuploadchunksend', function (e, data) {/* ... */})
.bind('fileuploadchunkdone', function (e, data) {/* ... */})
.bind('fileuploadchunkfail', function (e, data) {/* ... */})
.bind('fileuploadchunkalways', function (e, data) {/* ... */});