Is it safe for a foreigner to walk down Howard street in San Francisco

Virtually all of San Francisco is safe now. There is petty crime, especially vehicle break-ins, but random violence, muggings, etc. is very rare. There are areas of many homeless people, people who are on drugs or are insane. They can be scary and should be avoided but aren't a major threat.

Depends where. I wouldn't walk between 8th and 6th but from Embarcadero to 5th and from 8th onwards it's fairly safe!