You'll probably want to have more of a delay. The API rate-limits you, as you know. The list of rate-limits can be found here.

From what I could find, it appears that Tweepy gives you Basic Access. So, no more than 15 requests per 15 minutes. Unless I'm wrong about that, your sleep time should be at least 60 seconds (I would add in a few more seconds as a buffer though to avoid accidently hitting the limit)