Students definitely have to be on top of their schedule to make sure they are getting the classes that they need in the proper sequence.
My son had only a handful of AP units when he entered college and none of them were of any benefit. He also had very few “free elective” options in his four years. His schedule was usually packed each term and he was able to get the classes he needed, just not always at times or with instructors of preference. He will graduate on time in June with a degree in English and a minor in Fruit Sciences
My daughter in an Ag Business major in her first year, so her classes have been very regimented and sequenced for her. No issues getting into those. Ag Business majors, like many others at Cal Poly, are tossed into the major courses immediately and actually have a lot of their GE classes blocked into their upper classman years.
Take a look at the flowchart for your prospective major. If there are a lot of specific and prescribed classes associated with your major in the first couple of years, then you should have little trouble getting into classes in general.