The local TJ news says the San Ysidro border crossing is closed for those exiting Mexico due to a construction beam falling on car. I've heard it is likely the San Ysidro crossing will also be closed tomorrow, Thursday, September 15, 2011.
Local TV news reports showed people entering Mexico on foot. I think you can also enter by car, but suspect you'd wish you hadn't.
Traffic near the border is at gridlock. A friend spent 20 minutes without moving at the traffic circle near the border COSTCO (which was closed due the traffic problems).
My understanding is the Otay crossing is a zoo. Local news reports say traffic headed to Otay is backed up all the way to the Central Bus station. Local news reports say currently there is a five hour wait to cross at Otay.
As I post 20 minutes ago traffic on Agua Calliente was normal. My recommendation for those who have to return to the US now is to go to Tecate. I would take Auga Caliente/Diaz Ordaz to La Presa. There I would take the old road or the Via Rapida to the Tecate crossing.