In California, during rush hour, almost every off-ramp has a 'deceiver' holding a sign wanting a handout. They prefer hard cash. It's more of a business rather than a charity. If you come at the end of their 'shift', you may catch them behind a bush or under the bridge, splitting up their newly acquired large stacks of cash with their manager (aka pimp).
Giving cash to someone with your own free will is not illegal. But this off-ramp hand-out is a process usually built on deception and greed. They are pretending to be in need when in fact they are running a tax-free cash only enterprise designed to pull on the heart strings of well-intentioned people.
It's just too bad this scam has ruined my trust in people who hold up cardboard signs. I now only go through agencies or people I trust if I am asked for a donation. Those off ramp charities have become a group I loath and won't support.