Hiya,
I'm one of the people who prefers to use a walker (rollator, actually) at WDW instead of renting an
ECV or wheelchair. This is partially because I don't really have endurance issues, but do have joint issues and problems with standing in one place for more than a few minutes at a time. Your needs may be different from mine, so you may find that a wheelchair or ECV may be better suited to what you're looking for on your trip.
However, I can answer a lot of questions about getting around the parks with a walker. You can park them outside queues if you want but many rides will let you take them all the way through the line and leave them on the platform when you board. If you do use a walker on your trip, I would honestly suggest doing that instead of parking it, as some of the lines can be incredibly long (I think the line for Soarin' at Epcot is almost half a mile, if I remember correctly).
A lot of the newer rides have mainstreamed lines where they're wide enough to take mobility aids like walkers all the way through the regular line, but the Magic Kingdom still has a few older rides where you'll have to take a walker through the wheelchair access line because the general line isn't wide enough. The the three that spring to mind off the top of my head are Pirates of the Caribbean, the Haunted Mansion and the Jungle Cruise, though there may be others (I'm afraid I don't always ride everything).
I found having a rollator with a seat was extremely helpful to sit down in lines or while waiting for parades, since seating is a premium in the parks. It seems really difficult to find benches a lot of the time for some reason.
Regarding buses... it's sort of a mess right now. There's information in the FAQ, but when I went in October they weren't really following loading procedures like they did in the past. If you can't do stairs you can board via ramp or lift at the back of the bus, but it can sometimes be difficult to get the bus drivers' attention to let them know you need to board. It used to be that there was a separate handicapped waiting area for boarding and those people were loaded first, but they don't seem to be doing it that way anymore.
My partner and I went last October and we had some difficulty with the buses. Because the lines are mainstreamed, it can be difficult to get people to move from the handicapped seats if they've boarded the bus before you. Unfortunately, if you are not in the handicapped area, there is no other place on the bus for your walker that will not impede other passengers' movement, even if collapsed. This caused multiple issues when we boarded and I got to a point on the bus where I literally couldn't go any further, because I couldn't fit into the back "step up" area of the bus with my rollator and the people in the handicapped seats wouldn't move. I could sit or even collapse my walker until they did, and no one else behind me could get to the "step up" seats until the walker was stowed, so it held up the entire bus.
This happened multiple times during the trip and was incredibly frustrating. Several people on the boards are looking into the issue right now and hopefully Disney will be able to come up with a reasonable solution to accommodate everyone. I'm not sure how this differs from the experiences of those in wheelchairs and
ECVs, but I can say it was a detracting factor from using a walker/rollator in my most recent experience.
If you have any other questions, please don't hesitate to ask, and welcome to the boards.
