Private vs UC for CS

The UCSC class schedule https://pisa.ucsc.edu/class_search/ for fall 2019 indicates that the introductory courses were often over 90% full, but rarely completely full. So is it likely that a student who wants to fast-track CS courses will be unable to do so? The Northeastern class schedule https://registrar.northeastern.edu/article/schedule-of-classes/ for fall 2019 also shows high enrollment in introductory CS courses.