There were some good guesses on the mysterious scat question from this post, including several in the same mammal family, namely the Procyonidae (Raccoon) family: Coatis, Raccoons, and - Mark guessed it - Ringtails.
Linda Harris took the photo to the Desert Museum on her docent day. She writes:
Just by chance George Carpenter who is in charge of the Interpretive Animal Collection (IAC) came at lunch time to talk to the docents. He looked at the photo and said the scat has a high probability of being that of a Ringtail. There are Ringtails in the IAC collection. He said it is too small for coyote and coyote scat would have more of a blob, blob look and not a smooth look like this. Also Julia Strom, a former IAC employee, stopped by today by chance and said she thought the scat is Ringtail.Thanks to all who participated in this investigation!