Totally dependent on the employer.
To be safe, I would have a salary number in mind, just in case it comes up. But it really depends on the organization.
I would recommend not bringing it up yourself though, simply because if at all possible, you want them to make the first offer anyways, and if you bring it up, you are stepping into the obligation of saying what you are looking for, which is bad negotiating strategy.
In general, I think salaries shouldn't be discussed (at least beyond very general terms to make sure you are somewhere close to the same page) until you are pretty close to offering the job.