Here is an article from Palo Alto Online Community Resources: Web Link:
Household Hazardous Waste Program
Palo Alto residents may drop off photo chemicals, household batteries, paints, solvents, chemical drain openers, pool chemicals, household cleaners, aerosols, pesticides, insecticides, pharmaceuticals and hypodermic needles at the Regional Water Quality Control Plant, 2501 Embarcadero Way, Palo Alto, on City of Palo Alto Household Hazardous Waste Collection Days.
Actually they accept pharmaceuticals every day; I've just shown up to the office and they have a box to drop your drugs. They ask that you not drop off narcotics (but they do not verify your deposits).