In most parts of California, the education you get at a community college is comparable to that in your first two years at a four-year institution

I think this depends quite strongly on the institution, as well as your area of study (as you said). FWIW, I went to a community college for two years in order to save money, just as you said. I then ended up having to to re-take several classes at the university anyway, and thus lost a lot of valuable time (and money). I could be an outlier, though.