Can anyone tell me some of the bad experiences they’ve had at UCLA? Whether it be the workload, dorms, class sizes, social life etc.
try posting on the USC forum 
I am not a students, although many many years ago when I was very little my parents were grad students at UCLA. I will answer your question, however, because my son and I just toured the college and I have some opinions.
UCLA is a very very big and crowded campus with wall to wall students. The students were very active - hanging out, protesting, playing cards, etc but for me it was just so cramped and I felt somewhat claustrophobic and my son felt the same way, although he did not cross UCLA completely off his list. You have the be comfortable in this environment or it might be tough.
In the info session they talked about freshman class size - between 60 up to several hundred. Then class size reduces to around 30. Compared to the LACs we had visited that seemed huge. At the smaller schools they said classes from freshman year on up averaged 15 students.
Hopefully you will hear more from others but for us these were negatives.
HTH.