My unprofessional opinion: Same as every other September weekday.
Big dropoff, since it's a big boost in summer attendance.
You'll see more guests after about 5PM or so each night.
You are the exception.
There might be more attractions closed during the mythical offseason. Check the DL calendar.
There might be a shortened day here or there, for some private party. I don't see any in September except for on Fri Sep 28: DL closes at 7PM. DCA open until 11PM that night.
They start on 9/4 closing at 8PM Mon-Thu.
"Here You Leave the World of California Today and Enter the World of, um, er, California Today."
Thanks for that post. I was just about to ask if anyone belongs to TouringPlans.com anymore. I keep seeing all these "will it be crowded on ___? " posts and TP has great data on every day. They used to push it on this site. I think it's well worth the $6.98/year. No, I don't work for them.
Twenty years from now you will be more disappointed by the things you didn't do than by the ones you did. So throw off the bowlines, Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream.