Hello raulaguilarv.
Did you solved this problem? I am struggling with the same.
I was also trying to use this:
alert($('#quantity_wanted_'+ idProduct).val());
for debugging purposes, but no alert appeared at all.
EDIT:
I solved my problem, I hope it will be solution to yours likewise.
I have not default theme installed. And this theme has its own ajax-cart.js file located in module catalog. (This theme requires also a couple of modules and one of them is: responsivetopbar. And this topbar has ajax cart, which is handled via responsivetopbar module not, default blockcart).
My advice: use totalcomander, or something similar to find all ajax-cart.js or (when you won't find such another file) for phrase: .ajax_add_to_cart_button (for example) in content of your shop files. Maybe you will find out that there is another file which handles adding products to your cart.
Hope this would help somebody in trouble.