As has traditionally been the case, the schedule will be released before the draft. (USATSI)
A day after NFL spokesman Greg Aiello announced that the 2013 schedule wasn't yet finalized and "no release date has been determined," he tweeted this update:

Originally, speculation was the schedule would be released Tuesday, and NFL Network had programming built around that date. Not to worry, though: The schedule, as has traditionally been the case, will still be released before the NFL Draft, which runs from April 25-27.

The 2013 preseason schedule was announced earlier this month, and you can view it here.