we've been 2x's in october (just this past, and a few years ago).
This past october was wonderful - the first day though, they were having a cold spell, and it was about 50. We only brought shorts, flip-flops, etc. My toes were cold!! I had to buy ds a sweatshirt. Everyone was positioning when outside to be in the sunlight. We were laughing about it though. After it passed, it was probably 75 - 80 the rest of the week, and sunny.
A few years ago in october, they were having a heat wave, and it was 94 and sunny every single day. Everyone was positioning to be in the shade that trip. Still an awesome trip!
October can have a cold spell or a heat wave, or be just right. I'm a lot of help, huh? (lol). Seriously, I'd plan for about 80, but bring 1 or 2 capris/pants and a sweatjacket - even for the airconditioning in some restaurants. Or I always plan that I have to buy a clothing souvenir anyway, so if it's cold, I buy something long sleeve, etc (pants and socks are harder to find and fit though, so I'd bring 1 for each person just in case).
The lines were fine - not empty, not horrible. I think september is a little less crowded - some places have off school in october for fall break. just try not to do columbus day weekend (it will just be a bit more crowded - but that's any national holiday).
Have fun!