i remember saturday being the worst and sunday & monday not being so bad.
That was definitely not our experience in 2012 or...whatever year I turned 40 and we went for my birthday (the real Columbus day, which that year was on the celebrated day) and they were having the birthday celebration stuff.
We also have experience of two years being there for Memorial Day weekend (my son's birthday for two years in a row every few years).
Combined, we notice that crowds for weekends like that (and while Columbus Day is fairly ignored in many school districts around the country, there are breaks that tend to happen around there, and from what I've noticed CA school districts quite often do things that result in having the long weekend) grow as the week goes on towards the holiday weekend. It peaks on the weekend, and those crowds are still there for the most part Monday morning.
I got to fight my way through the crowds on the Monday holiday last year, when our plan had been to avoid it all, but a musket DS had bought was broken by the time we picked it up from DLH bell services after having the store send it over. It took AGES to get through bag check (and I'm still holding a grudge against the young woman who did the "oh I'm just looking for someone, oh I'm just peering through the crowds, oh I'm totally snaking into line ahead of at least 50 people and I'm just going to sneak through" move) and absolute ages to get to the store (the Pirates League store stashes the seethrough neon green pirate muskets, by the way...they were gone from every other store because PL snags them).
But from my birthday experience and both of DS's Mem Day weekend experiences, the crowds diminish through the day, and the rest of the week lightens as well.
We also went in July twice last year, and crowds were NOTHING compared to what we experienced last year that weekend....