Castelrotto/Bolzano in Late May

That is exactly the time I went about 5 years ago. There were virtually no tourists, the weather was very nice, and we were able to drive right up to the Alpe di Suisi (sp) after 5:00 when the few tour buses that were there left, and hiked along some of the paved trails. We drove on a road way up in the mountains, it was very cold when we arrived at the pass, but we were in a warm car, and the fews were stunning. It was a cloudy evening, but right about 8:00 pm the sun broke through the clouds and illuminated the peaks. It was breath-taking. Every season has something different to offer. As I mentioned in another post, we just knocked on the door of a home that advertised B&B (however there is some other German word for it)and stayed there. It was clean and a lovely home. They didn't speak English, but had a HS daughter that spoke a little. All was well.

We stayed in Castelrotto for 4 days at the very end of May a few years ago. We took the bus ride up to the Alpi Suissi ( It left quite often throughout the day from the center of town). We were able to do one great hike and it was beautiful. The other times it was snowing and very cold. It was beautiful to see but we didn't hike it.
The town was very festive when we were there as they were having their Renaissance Fair. Lots of fun.
We stayed at at a B&B on the outskirts.
We took the Dolomites drive and the passes were open but not many people around and rather gloomy the day we did it.