There's not one specific answer to this question.
The holiday season will "officially" begin this year on Monday, November 14. That means that 75% of the decorations around the whole Resort will be up and all the holiday entertainment (Christmas Fantasy Parade, Reindeer Round-Up, Believe in Holiday Magic fireworks, Santa, nighttime Winter Castle, snow falling on Main Street, It's a Small World Holiday) will be up and running. Both
Disneyland and California Adventure will be decorated but the 3 hotels and Downtown Disney will not be. There will be holiday treats and merchandise sold.
After Thanksgiving is when the 3 hotels and Downtown Disney get their decorations as well.
Before November 14 - and you said you may be there 11/9 - 11/12 - you will see most of the 2 parks' decorations. They start to go up a little at a time, in late October or as soon as November begins. Most of the seasonal munchies will be sold. Haunted Mansion Holiday will be open. But you won't get any of the other official holiday entertainment, except for
possibly a "soft opening" of IASW Holiday, during your trip, though that soft opening can't be counted on.
So, basically, if you just want a taste - a sampling - of the holidays at Disneyland Resort, you will get it. But you won't get the full holiday experience.