Really depends on the time of year and the actual year. I lived right on the path of the camino and talked to tons of people who were completing it. "Holy years

Really depends on the time of year and the actual year. I lived right on the path of the camino and talked to tons of people who were completing it. "Holy years" will see about 1.5x to 2x more pilgrims. It peaks at el dia de santiago (July 25). That's when the trail, particularly the last leg, will be quite crowded. On July 25th it will be a steady stream flowing into the main square. In late summer, fall or spring, from what I gather it's quite easy to not see a soul on most days. There are also a lot of side routes off the main path. Also, although the route has a lot of religious meaning, loads of people who are hiking aren't religious at all. So don't let that discourage you.