The way I understand it, most of the recruiting rules for JC players are no different then those for high school players.
If the player doesn't have any interest from a D1 team by the end of his JC years, I think walking on would be very difficult if not impossible. If no D1 interest is shown, the player should consider looking at/contacting D2/D3 schools. Many D2 schools in CA have a lot of JC transfers/walk-ons. The JC players coach should be able to help with D2/D3 schools.
Another alternative is to attend an on-campus prospects camp.. however I imagine there aren't a lot of prospect camps remaining (easter?). You'd have to check with the coach to see if he'll allow a JC player at the camp.
At the very least the player need to arrange a decent summer team ASAP to keep the process alive as many schools recruit JC players all the way up to the start of the fall term.
btw 4 year coaches can attend the player's practice and often do at JC's because they are able to see more then one prospect, unlike high school.