Go! - Absolutely Go! I went down for just the day last year, and it takes me around 2 - 2.5 hours to get to Baltimore. It was worth it. There were just so many beautiful, inspiring things - and then the yarn - oh the yarn!
This year I decided to take a few classes too - and stay over in the area. I can't wait!
And I think I just registered online last year - you can pay a small fee just for the Market, and there are Market Sessions too, for about $30 for a hour long session, if you have any interest in that. If I remember right, the fee for the Market was around $5.