My wife and I left St. Jean on Dec 15, 2010. We had gorgeous weather for most of the Camino all the way to Muxia. We climbed to Roncesvalles under mostly sunny skies and descended the following day, in light snow, to Zubiri. Fantastic. Judging by the time you have to walk you should have no problem completing the first half of the Camino. I would imagine that you would be around Sahagun on the 4th (mas o menos). We found the Camino very quiet until Puente la Reina when we picked up a few other pilgrims. As we traveled westward those numbers gradually increased but I don't think we ever had more than 15 (or so) in our group. We spent Christmas Eve in Santo Domingo. Had a fun dinner with 6 other pilgrims. You will have a great Camino. We are leaving St. Jean Dec 31st for another trip to Santiago, Finisterre, Muxia, and maybe the Camino Ingles. Good luck.
John