One of the most culturally vibrant, high-tech, and overall exciting places to visit in the Bay area, San Jose is a MUST SEE for your group while in California.
San Jose is the capital of Silicon Valley, a major tech hub in the Bay area. Attractions such as Googleplex, Apple Park, and Adobe Semaphore greet you on this front, as will San Jose State University, a great tech school. Outside of the tech world, you will find fantastic architectural landmarks and historical buildings, such as the Cathedral Basilica and History Park.
Downtown San Jose is home to excellent shopping, dining, and entertainment options, from the San Jose Flea Market to Santana Row. Theaters, museums, and galleries await all throughout the streets, as well.
For some 'natural' fun head to Mission Peak or Lick Observatory within the Diablo Range and catch some of the greatest views of the valley available.