Hi Kate! San Jose is a huge city, but I'm guessing he'll be staying in or near down town? There are a TON of restaurants in that area, as well as being near the HP Pavillion, where lots of events (hockey games, concerts, areana football, etc) are held. There is an IMAX theatre, a discovery museum, and a couple of venues (other than HP Pavillion) where shows, concerts, or comedians perform. All of this is within walking distance for the most part. If he's staying at a decent hotel, I would really refer him to his concierge for dinner recommendations, simply because of the shear volume of places to chose from down there.
Hope he has a great trip!