Most hikers go northbound. Though there will be some faster hikers coming through earlier, the main part of the herd will be entering southern Oregon during your first 2 weeks on the trail. So if you go south, you'll likely see very few people the first several days and then start running into the herd hiking the other direction, passing you by in ever growing groups. If you go northbound, you'll see hikers from the very beginning passing you behind as you hike north, with the amounts growing every day, though you may stay ahead of the largest group. It really depends on the snow situation in the Sierra Nevada as that defines how early most hikers reach Oregon. A PCT thru-hiker will likely hike the entire state of Oregon in the time you are just doing the northern half, so you'll likely never see the same person twice unless they are a section hiker like yourself.