Would any of the UCs let you major in molecular and cellular biology and minor in bioinformatics?
Yes. Not sure which UCs have a bioinformatics minor program going, but it only takes a quick search (i.e. bioinformatics minor (insert UC here)). From what I saw, UCLA has a bioinformatics minor and you could major in MCDB or bio.
Alternatively, at Berkeley, you could major in MCB from L&S and minor in bioengineering from COE with a focus on computational bioengineering (same thing).
let you… funny.
BS majors/minors tend not to be quite that focused but, most colleges of any size allow you to build your own major.