It's varied a good amount by batch, but for our past couple batches, we've gotten a few hundred. That said, I don't think looking at raw numbers is particularly useful, because many (most?) of the people we say no to fall into one of these categories:
* the applicant says he/she wants something very different from what Hacker School is (e.g., a highly structured curriculum, some sort of "startup school", etc)
* the applicant doesn't appear to actually like programming
* the applicant didn't take the application seriously, or provided little to no information in the application
If you have a clear idea of what Hacker School is and you're a smart and friendly person who enjoys programming (whether you've been programming for two months or ten years) and want to get dramatically better, your odds of getting in are pretty high.