Though I don't practice in your state, I agree with all the comments made and defer to the attorneys' knowledge of CA law. I would suggest, though, that you take photographs of the area, with and without the boats/vehicles that block the easement and show how they block the easement and mailbox, and make it difficult to enter your homes. This will help the attorney understand your situation, and may also help a mediator or judge when the matter needs to be resolved.