We will be driving through during the running of the bulls, but will not arrive early enough to see it. Is it still worth stopping there for the afternoon?
It sounds like you're going to only pass through during one day of San Fermin and not spend the night. You know the bulls run several days, right? If I'm correct, skip it. Pamplona is a neat place and well worth a couple of days. The problem with your timing is that all you'll see is a jumbled, littered, crowded mess without having seen the reason for it.