i think you should take your basic/core math and physics classes for fall and winter quarter. after that, talk to people on campus, some of your professors, your academic/pre-major advisors. and also, consider which of those classes you like, which classes you want to take in the future. that way, you have a foundation to base your decision on
unless there is an entirely different track of courses for the first year, you should be fine holding off your decision for a couple quarters
edit: while you should talk to your advisors, it's really your choice in the end. and, i don't have personal experience yet, but I have heard that academic and pre-major advisors are quite useless. i guess you will find out then.