The blog in my sig is a little over a week old. I was wondering when is a good time for a press release?
It's never a "good time" for a press release until you have real news to share. Launching a blog isn't newsworthy. Do something newsworthy with the blog, address a problem no other blog is addressing, fill a need in the niche, do something related to timely issues in the niche or industry, etc. Only then should you really be thinking about a press release.