Monterrey Bay is good, I'd suggest going to the boardwalk as well.
No, the Tech Museum is mainly for little kids IMO. There is a small Intel museum ( about 45 mins max time spent there ) and a Computer history museum that I have never been to in San Jose.
Edit: If you can, go to San Fransisco. They have many things over there ( Academy of Sciences, Golden Gate Bridge, Ghiradelli Factory, ect. )