Sheese!! Everyone just get a passport. It will make the border line faster for everyone. It's not that hard. And for all of you that are going to cross back without one make sure you go thru TJ, so the rest of us don't have to wait because you were too lazy to get one. And enjoy the wait at secondary.
I don't know where ocotilo got the info, but I called the Mexicali Port of Entry last month and was told the same thing. They also told me that you could show your receipt if you had applied for, but not yet received, your passport in the mail.
City of Chandler main clerks office on AZ ave/Chandler... They can process your paper work there... Download all the paper work/fill it out first, then drive down there and get in line..... it didn't take too long, less than an hour on a friday afternoon..