We stayed at Poly last week and they had lots of open tables every morning when we passed.I think you would be fine walking up for breakfast.We also got 2 walk up adr for dinner there with no problem.
It depends of the time of year. Breakfast at Kona Cafe rarely fills, and you likely will be able to get a table without a reservation. But during the busy holiday seasons and even during the free dining promotion, every restaurant becomes crowded, making your chances unpredictable.
If you have an idea of what day you would like to eat at Kona, I suggest making a reservation. There's no harm in having one, and you can easily cancel if your plans change. Otherwise, just wing it and see what happens.
We eat there every morning when we stay. Sometimes we have to wait a few minutes, even when the place is empty, other times you are seated immediately. We are usually there around 7:45-8:15 and do not usually have to wait long in the first week of October. Any later than 8:30 the place begins to fill up though.
They open around 7:30 usually - if you get there around then or shortly thereafter you might can walk in, especially during slower times of the year. During busy times? You might very well be turned away.
ADRs are ALWAYS the safe way to go anywhere in WDW - resorts or parks.
We never made reservations and the longest we waited there was about 5 minutes. Then again, we were only a party of 2. It could go either way I suppose, but if it isn't much trouble, you may want to make reservations just in case. Good luck!
We always make an ADR, last trip we went to Kona for a late breakfast- 10am and the resturant was pretty empty. We were planning on the same this trip (October) and thought we could probably wing it. After reading some comments here I just decided to ahead and make the ADR, if we want to change the time we probably could when we get there. Why spoil a relaxing meal by having to wait a long time for a seat...