Hello Sydney! The Disney Parks Moms Panel has a wealth of knowledge between us all... and it's not just for moms! I'm a mom, but I am also in my 20's and have taken several trips to Walt Disney World without my family.
It is still warm in October, so my first suggestion would be to pick a resort that you think has a great pool! I personally love staying at Disney's Caribbean Beach Resort or Disney's Polynesian Village Resort. When I am on trips without kids, I love to sleep in a little bit and relax by the pool in the mornings. It's fun to stay out late at Walt Disney World and I love taking advantage of the late night Extra Magic Hours in the Parks.
One of my favorite stops at Walt Disney World when I don't have kids with me is
La Cava del Tequila at the Mexico Pavilion in Epcot. They have some of the very best margaritas I have ever tasted! I recommend the avocado margarita to everyone. It is that good! They also have great chips and salsa and guacamole. La Cava Del Tequila is such a fun place to hang out in, perfect for anyone in their 20's.
Jellyrolls on Disney's BoardWalk is a fun place for the 21 and over crowed. There you can listening to dueling pianos and participate in audience sing-alongs. It's a very popular nightlife spot at Walt Disney World and can fill up quickly, it is normally standing room only by 9:00 p.m.. Hours are generally from 7:00 p.m. - 2:00 a.m. Don't forget to bring some cash with you and request your favorite tune!
I also really like to ride rides when I am on an adult only trip. Sometimes, on bigger rides like Rock "n" Roller Coaster Starring Aerosmith, I jump in the single riders lane and have little to no wait and ride again and again.
Happy Planning! If you have any other questions, please ask!