Girimama33 -
Looking at your first few questions, I have a hunch you may have seen my reply in yet another MHP-related questions thread last night!
But I will repeat some of what I posted there in this thread too!:
I went to the MHP on a Monday night last year. It was only the second party night of the season. I found it to be much more crowded than I expected - not unbearably so, but it was not slow or quiet by any means. It looked like a weekend night.
The lines for most characters were pretty long. There were long lines for certain rides but not others. The long lines moved pretty fast at the treat trails.
(I have also been to the older version of the party - when it was still being held in DCA - on a Friday, and it was pretty much the same thing.)
There are many treat trails around
Disneyland - and then treat stations along each trail. Some of the lines at the trails and stations are long, but they move faster than you'd expect. Last year, for example, there was a treat trail (with several treat stations) in the Pirates queue (because Pirates was closed for 2-1/2 months last year). That was a long line but it zipped right along. Likewise with the trail at the Golden Horseshoe (which has a few stations) - long line; moved quickly. Innoventions had a line but it went fast.
Pixie Hollow did not have much of a line at all - I think a lot of folks skipped that trail altogether or didn't notice it!
There were also not really any lines at the trail back at the Halloween Round-Up.
As for Halloween Screams, we watched them. We arrived probably about 30 minutes beforehand, I think. Lots of people were already camped out. We were facing the Castle, but off to the right-side and back a ways. The view was okay.