There are several options for local dialup service at WDW. You can use a "free" trial of AOL, but you'll spend lots of time "cleaning" your computer afterwards of all the pop-up junk you loaded with the "free" installation.
You can get a free service - like netzero or juno (I'd download it on the computer from home and you'll be all set once on site). There are also prepaid services that offer local service at WDW. (Budget dialup is a good one).
You could also just call an Orlando local ISP and pay for a month's service (shoudl be no more than $20) to use during your stay.
I use netzero at WDW and it works fine. Just make sure the dialup number is truly a local call. There is a list of local prefixes in the villa phone directory and you can also check with the resort operator. (You DO NOT want to use a long distance number with all of the surcharges at the resorts.) Use a number for Reedy Creek and you should be fine.
Enjoy!