Legal Question in Real Estate Law in California

You would have to check with the local jurisdiction about that. I'm guessing it is state land, in which case you would have to check with the local state parks office. I would bet, however, that it is illegal, at least without a permit.

Maybe with a proper business license and permit.

What's the small handy object? A joint full of marijuana?

Two separate issues here. Selling stuff in parks is regulated by the park operator (city, county or state), probably requires a permit, and they can be tough to obtain. Distributing flyers may be a matter of First Amendment free speech rights, much more difficult for the park authorities to control, but nevertheless they may have a right to restrict handbill distribution on the basis that your handbill is only commercial advertising and leads to littering, and that those concerns outweigh your right of free speech.