Just a quick update for posterity:
Yesterday, I ran my first mile in 13.58 minutes.
Previously, my fastest mile was "14-something" in high school. Now I can definitely state that this was my fastest mile ever. Of course, I celebrated with shin splints and a blister on my in-step caused by my insoles shifting.
The official training plan started this week, which means tomorrow is my first Saturday outdoor run. It's only a mile, but I know "real" running is slower than treadmill running. I'll be happy to finish it in 15 minutes.
I need to grab my paperwork from the gym and start a progress chart. I started exercising the first week of April, and when I first started my interval training my mile time was right around 16 minutes. That means I dropped 2 minutes off my time in 2 months. I realize that's a progress curve that'll start to level off, but right now I'm pleasantly shocked at my progress.
Now I just need to string 9 more of those together and I'll be ready for my race! 18 weeks to go... yikes!