We are recent DVC members and have decided that we will go down for one week each in October and May. We couldn't decide so we're doing both.
Actually, we went the last week of October in '02 and we will be going in May for the first time this May 4th - 9th. We ourselves are curious about which we will like better so we can let you know for sure when we get back.
I have to say that the last week of October was very nice. Do you really get in the spirit of Halloween? We attended the
MNSSHP in MK as well as the Halloween party @ the Boardwalk. Our 3 yo dd loved both! Also, there is the Food and Wine Festival in Epcot. If the idea of walking around the WS sampling food and drink from around the world appeals to you, then you will thoroughly enjoy this event.
The weather was unseasonably warm when we went -- in the high 80's, which made BB very crowded as it was the only water park open the last week in October. From what I've heard, highs in the low 80's is more typical weather for that time of year. It rained only one day the week we were there. Crowds were light except for the slides at BB (probably wouldn't have a problem 3rd week in Oct. if TL is open) and the HM in MK.
My understanding is that the weather we experienced was more typical of early May. Since we love all of the water activities, we are happy that the beginning of May is typically warmer than the end of October.
Of course there are no Halloween parties in May, but there is the Flower and Garden festival which is supposed to be nice.
All in all, you've picked two lovely, comparable times of year to go so I can see why your decision is tough (we couldn't choose either). My best advice would be: if you are die-hard water park fans and don't care a lot about Halloween, pick May as you are more likely to get warmer, sunnier weather. Otherwise, I'd pick October as you get so much bang for your buck: the Halloween parites, the Food and Wine Festival, low crowds, and probably pretty good weather too. (Of course, when we come back from our May trip I may suggest otherwise)
Anyway, good luck with your decision and let us know what you decide!