From The Las Vegas Review-Journal comes their on-line edition of what to do during Halloween in Vegas. http://www.reviewjournal.com/media/interactive/halloween_events_09/
The Las Vegas Sun also has some information as well: http://www.lasvegassun.com/news/2009/oct/20/guide-halloween-las-vegas/
I have walked the Strip the last 2 years and it was very boring. Hardly anyone was dressed in costume.
Now, Halloween was on weeknights, so I am sure that has something to do with it. With Halloween being on a Saturday, this may change.
The weather will be beautiful, about a high of 74 and a low in the mid-50's.
But just remember, don't drink too much or else:
