When I was at community college (~ 2000), if the section you wanted was full at registration, you'd register in another section (in case), but show up at the section you wanted and talk with the instructor. Depending on the course/instructor, you'd might need to show up for the first week and anybody who hadn't attended in the first week would be dropped and those who had attended but weren't registered could take those spaces. Sometimes the instructor would do that at the first meeting. You'd go to the section you were registered in as well, and let the instructor know there (sometimes it'd be the same instructor and then maybe you wouldn't need to attend both sections). Not ideal, but registration order was based on completed credits, and after one semester it got a lot easier to get into the sections you wanted; students (real or not) that haven't completed any classes get to pick sections last, so once you've shown you're willing and able to complete classes, you're good. (Protip: check if taking any class in the summer will help you get into the sections you want in the fall)

At that time, you could drop classes in the first two weeks for a full refund.