We were just there Oct. 11-15 (Sun-Thu). This bridges Columbus Day weekend and some AZ fall breaks. I had a last-minute panic because the Friday beforehand the park hit capacity (my guess is buzz from the new fireworks and Ghost Galaxy got a lot of AP holders out), but we found the weekday crowds OK and even better than some past spring-break weekdays.
The Monday (Columbus Day) had "weekend" park hours and showed Fantasmic twice, which was great for us since we wouldn't be there over a real weekend. Crowds were there, but using Fastpass well I think the longest line we had was about 20 minutes for PoTC. It was colder and rained on and off on Tues and Wed, which gave us great low crowds.
Unlike WDW,
Disneyland doesn't do all of its entertainment every single night in the off-season. I would say to plan a trip for being in the park at least one weekend night if you want to see Fantasmic (and not knowing when the new World of Color will be showing, maybe another night for that), and some weekdays. Like Tuesday through Friday, or Sunday through Wednesday. That way you get the entertainment but have some lower-crowd days.
I had a friend who was there the last weekend in September when they debuted Ghost Galaxy and the new fireworks and she said it was nuts. I don't remember the
Southern Calif APs being blacked out on weekends last year, but they are this year. Might have some effect?
I thought the Halloween stuff was wonderful and some of my favorite things from the trip -- Haunted Mansion, the fireworks, Ghost Galaxy on Space Mountain.
PHXscuba