We went about 5 yrs ago at October Half term. It was my first trip to DL and I loved seeing all the Halloween decorations including Haunted Mansion decorated as Nightmare Before Christmas and Space Mountain as Ghost Galaxy.
We did the party one evening and just bought a ticket for the party that day and went to Knotts during the day. To be honest I didn't really notice the Halloween decorations at Knotts but there was a party on that evening and there were hoards of teens waiting to go in for the party - they make everyone leave and then re enter for the party. There were some areas roped off ready for the party which I understand is more intense than the one at DL.
We decided not to take Halloween costumes to wear for the party due to the logistics of taking them from UK (especially as I had to pack in secret as DD didn't know anything about the trip until we were in the hotel the night before) however we decided to just wear 'crazy' instead. We took hair glitter in various colours, glow in the dark nail polish, Halloween tinsel, Hairbands with spiders dangling from them etc. We got a few comments from CMs during the evening about our hair and it was an easy way of 'dressing up' without too much hassle. It was a fun evening and the Halloween fireworks were really good I seem to remember. We also collected bags full of chocolate, sweets etc