I would like to suggest an improvement in the C4P workflow.
When a proposal is submitted in the web form (http://2015.es.pycon.org/es/proposals/submit/), the user does not have any way to make sure that the proposal has been successfully stored, and the user cannot later check about the proposal details in order to see if anything is wrong.
The ideal (although complex) solution would be to have a user management system for the web, so that the user needs to be logged-in when submiting the proposal. After the submission,the user can check the proposals and edit them if needed.
A simpler solution could be just e-mailing the user acknowledging the reception of the proposal. The e-mail text will also have the details of the proposal, so that the user can have review them later.
In case the user need to change anything (anything important) in the proposal, an e-mail address could be included in the e-mail so that the users can write to that address if something important has to be changed / updated, and a system admin can change those details directly in the backend.