No Adr's and getting in where/when you want depends on a couple things.
* First of all are you a party of 2, 4, 8, etc.??? Obviously with a smaller party I would imagine it would be easier to get a table on a walk up basis vs. being a larger party.
* Also busy season vs. off season. If you are traveling during a school vacation, spring vacation week the parks will be more crowded thus restaurants having less availability. Also check and see what promotions are running while you are there - our trip in October they are running the
free dining so I anticipate it will be a little more difficult to get some ADR's as many more people are eating sit down meals vs. counter srv meals so you be better off at least trying to plan some ADR's in this instance.
* Traveling with kids vs. w/o kids. I wouldn't want to be in the predicament of having young hungry children and not able to find a sit down meal when you want to eat. If it were just me and dh we would wing it as we really wouldn't mind if we had to find somewhere else to eat. But to tell DD that we will eating with Cinderella only to be turned away
* Hard to get seating - advanced or walk up - would definitely make an ADR - If you HAVE to eat somewhere for whatever reason - CRT, Cal Grill to watch fireworks, etc. I would make sure to make those ADR's so that you are guaranteed a slot.
I like to have a basic plan - this park on this day with maybe 1 ADR planned in the same park - it can be cancelled at any time - 24 hr advance needed for a couple like CRT - but better to have 1 ADR and cancel than no luck getting in anywhere else.