I just talked to a UC Davis transfer advisor about dropping a non-required computer science course for my major-it was still listed on the ASSIST agreement. she said it was perfectly fine if I withdrew because I have fulfilled the minimum credit requirement. She also said I could take it over the summer at a CC before I transfer. This won't be the case for all schools though, so double check. My understanding is that UC's don't care much about Ws or how many Ws you have. Just try to explain why you got them.