Whatever your misgivings, do make the call. In the case of a homeless man or woman with a substance abuse problem, you might otherwise see more incidents of petty theft, as drug addiction and crime often go hand-in-hand. More importantly, letting someone lie on the sidewalk for days is simply not humane. Many homeless people suffer from mental illness and need medication. Ignoring a person on the basis that he or she is "not bothering anyone" is to renege on a fundamental human responsibility.
 
If you are interested in going a step further and volunteering, visit the Web site for Project Homeless Connect, a monthly mobilization of volunteers and professionals trained to link the homeless to a range of services. The hub of the event is the Bill Graham Civic Center, where people can get medical treatment, counseling, food, information on housing, etc. You may volunteer with any one of Project Connect's various teams: street outreach, client support services, triage, food, activities, or transportation. Volunteers gather every month for a "mass mobilization" but actual "Outreach Events" for the homeless take place bimonthly. 

You also can make a tax-deductible financial contribution to Project Homeless Connect at SFGoodWill.org. See Project Connect's Donate Page for a list of requested product donations, which are also tax-deductible.