If only we could turn those two street/traffic signs around!
If it's the same location as the phone number on the sign, OV-60791,
the OV exchange is in Montebello. (OV = Overbrook)
Per: Old Telephone Exchange Names / Los Angeles County
http://www.laalmanac.com/communications/cm01e.php
Montebello does have the Montebello hills so that wouldn't surprise me if this was in fact Montebello.