Returned home 6 weeks ago, and you will find the Valcarlos route a very enjoyable walk with minimal time spent on the busier highway portion (as commented above you do not feel at risk during the day). The route was fairly well marked with the trail exits from the highway very clearly marked. When you do walk along paved roads before Valcarlos, most of this is on quiet country roads through farming communities...a beautiful introduction to your Camino experience! Arrived in St. Jean in the afternoon, and with jet lag abounding decided to stop the first night in Valcarlos, which proved a good decision. The next day was a straight forward walk/hike (unfortunately through heavy rain and cloud) partly along the highway (very little traffic), but mostly along lovely, wooded trails. It wasn't a difficult walk, but this of course is different for everyone...on arrival you may find yourself bursting to begin walking as I was, and the walk just seems to fly by. Those walking the Napoleon the same day were unfortunately caught in the same rain storm, slippery mud (decending into Roncevalles) and were unable to enjoy the panoramic views. I saw only one other pilgrim in the two walking days well back behind me as I exited Valcarlos, probably because of my departure times from St Jean and Valcarlos. Hope this helps.