Ok... my experience with cell phones in WDW has led me to only trust AT&T national... never had any problems!
Now about 2-way radios... your not going to find a cheap 2-way that will pick up a signal if one is in AK and the other is in MK atleast not a good signal. I have many diff 2-ways (I love to mountaineer) so let me give you a few suggestions of which ones have worked well for me overall. First let me say DON'T BUY CHEAP, they work when they want and like mentioned earlier with the amount of buildings and other obsticles you wont get great performance...
1) Motorola talkabout T5820... pretty good range, plenty of channels both GMRS/FRS, 5 mile range, found them to be pretty clear. I believe around $99.00 for a pair
2) Motorola talkabout T7200... a bit on the big side, full of fancy options, but completely clear, I relied on these when I was in Nepal and they worked better then motorola said they would... I was picking up signals at 10 miles.... these retail at $130 a piece but worth it!
3) I just want to throw this one in because it is my new favorite... the Garmin Rhino 120. So this is a 2-way/GPS which is not needed for WDW but can be a lot of fun. I use this for backpacking but I took it to WDW and it worked better as a 2 way then any other I have used... I talked to my brother who was at Stormalong bay while I was just barely getting off the freeway from the airport to go to WDW... these most likely aren't what you'll even look at but you should they retail at $250 a piece, they work great and what was really fun was getting home and finding out that my nieces had left them on while we were in the parks and now we had a record of where we walk and when for our whole trip... I LOVE GPS!!!
ok anyways... study up on these... don't just buy b/c you found some for a good price... if there cheap they will work cheap. Good Luck!!!
Justin
PS. I forgot to add... if you decide to go with a lower model you should be fine getting them at Radio shack or Wal-mart... but if you want to purchase one of these that I have mentioned or any other with a better frequency I would buy from an outdoors retailer... REI, Galyans, Cabella's, etc.