The stadium is across the street from Santa Clara Train Station. CalTrain goes through familiar peninsula towns from San Francisco to San Jose. In San Jose, visitors may catch the Capital Corridor to Sacramento.
A sightseeing hint - you might want to include extra time and see the beautiful historic Santa Clara Mission which is also on University grounds a very short distance away.
I waited far too long to experience this local action in town. San Jose Earthquakes has a big presence with the Silicon Valley international influence here. I do recommend!
Oh, I will be adding restaurant recommendations you may go to before games - I must say Chili's on El Camino and Lawrence Expressway has very tasty chicken nachos and Patron Pomegranate Margaritas and is quick.