I was considering the Math/CS major at UCSD as well, but keep in mind that is it not really a replacement for Computer Science. This link sums it pretty good:
http://www.reddit.com/r/UCSD/comments/21rmu9/help_with_colleges_difference_between_the_cs/cgg6u2w
From what I’ve read, it is more of a Math major than Computer Science, so it’s feasible if you know what direction you want to go after college (Math/CS would be good for data science or areas where more math is needed). Math/CS can definitely land you a software engineering job, but employers will probably want to see more projects/experience on your resume and ask you more technical questions since you’re not a “pure” CS.
I decided to TAG to UCI and spend an extra year there instead of an extra year at CC to meet UCSD prereqs, but it’s all up to you! 