We used to go in October but it seems the month has gotten progressively more crowded so I am not really sure which would be the least crowded part of the month. Just guessing that the first week is when all the Halloween activities are starting to kick in so it might be a bit more crowded than mid October. I would also asume the last week might be busy with everyone trying to get in one last visit for Halloween festivities.
HM is up and running with it's NBC overlay by the first of the month. The park is pretty well in full Halloween decoration by the first of the month. Still too early to tell what might be down for refurbishment.
As far as events that might add to the crowds, here's what I found listed (from one of those other boards) on their calendar for last year:
October
Gay Days at
Disneyland (unofficial event) Friday, October 5 through Sunday, October 7. Event attendance will be higher at Disneyland on Saturday, DCA on Sunday (link).
Mickey's Halloween Treat. October 5, 12, 19 and 26; 7:30 PM - 11:30 PM and October 4, 11, 18, 25, 29, 30, and 31; 6:30 PM - 10:30 PM Tickets are $39 per person if purchased the day of the event. $29 advance-purchase tickets currently available through the Disneyland Web site (click on the "tickets" link). $27 discounted tickets are currently available to Annual Passholders via the Disneyland Annual Passholder Web site, and to Disney's Vacation Club Members at the Disneyland Resort ticket booths.
MousePlanet night at Mickey's Halloween Treat (unofficial event) Friday, October 12. Join your fellow MousePlanet readers and MousePad members at Mickey's Halloween Treat to kick off MouseAdventure weekend. More information is available on our MousePad discussion boards. (Link)
MouseAdventure. Sunday, October 14. Registration is now closed.
CHOC/Disneyland Resort Walk in the Park Sunday, October 21 (link)
Nevada Day. Friday, October 26. All Nevada public schools closed to commemorate the admission of the state of Nevada into the union, possibly resulting in unusually high crowd levels at the Disneyland Resort. (link)
2007 UEA convention. October 29 to 30 (in Utah). Many Utah public schools close so teachers can attend the Utah Education Association convention, which creates a four-day weekend for the students. Expect the resort to be busy that weekendsome claim 'UEA' stands for 'Utah Escapes to Anaheim.' One reader has told us that his Utah school district is closed for a "Fall Break" October 11 15th, so crowds may be more dispersed throughout the month than in past years.
I do remember that weather is fantastic at that time of year. Hope you have a great time whenever you decide to go!