However, keep in mind that some schools say that they only want you to send LORS via AADSAS. When I emailed Columbia, they said that they "strongly prefer" letters to be sent via AADSAS, but I am not sure if that meant that they will NOT TAKE letters from the UCLA Career Center. All in all, I sent mine directly to the schools from the Career Center.
But it also takes them a few weeks, so prep for that. I submitted my LOR request at UCLA on August 12, and they are still pending. They said that they should at the latest be mailed out on August 31st.
Good luck!