I am planning to go this year (it is quickly looking to be the once a year pilgramage). I don’t know about the hotels because one of my friends lives a couple miles from the con, so I am staying with her and her husband (They are also GWC listeners, but doesn’t post).
I can tell you that I stayed in one of the overflow hotels and it was about a 6 block walk to the con hotels. I also know people who stayed a bit closer, but were not at overflow hotels.
If you want to stay at the con hotels I would say book NOW. If you don’t mind a little walk the overflow hotels are slightly cheaper (we paid about $100/night).
My other suggestion - get there Thursday and don’t plan on leaving until Monday afternoon. This is a little easier if you are driving, but I missed half of the first panel because of a late plane (not mine, someone I was meeting) and the last panel (because my plane left too early).
Also - prepurchase your tickets - the line is MUCH smaller and quicker.