Seems like a lot of advisors say this, but lots of students at Berkeley do fine starting in more advanced math courses. Since the math department puts old final exams up on its web site, an entering student with AP calculus credit can easily check his/her knowledge of Math 1A (or Math 1B) material by trying these old final exams to make a more informed placement decision: https://math.berkeley.edu/courses/archives/exams
However, a student who took calculus AB, or took AB+BC over two years should be aware that college math covers material twice as fast as those high school courses.