If you are worried about a rainout this weekend, then based on the last rainout (1st game of the SF series), what they do is allow you to go to the make up game without any further action, but if you do not want to go the makeup, they allowed you about a month to swap your tickets for any remaining game, subject to availability. I am not sure there are blackout dates, but I suspect that if you wanted the 7/4 11 AM game vs. the Dodgers, you'd have to act fast.
All this is assuming they adopt the same policy.
