<<" As I understood it, going to Wengen and Jungfraujoch would be a biggamble in May because of the elevation and some hotels may not be openuntil the last few days of May. The closer it is to June, the morecooperative the weather might be. For that reason, I decided toleave Wengen for the latter part of my trip, even though it's still noguarantee that I'll be so fortunate to experience sunshine and clearskies. ">>
I am considering staying in Wengen at about that time, and one of the nicer and more expensive hotels ( Hotel Schönegg) opens on June 3rd
But, there will definitely be hotels that are open, either in Wengen, or Grindelwald or Lauterbrunnen or Mürren. And, at the end of May, I am sure thatthere are not hordes of tourists filling all of the rooms. If I were considering that time and place, I'd ask about accommodations describing your price/style preference in the forum section about Accomodations,
then check with the hotels that Arno and Annika can suggest.
Arno and Annika know the region very well, and surely can help with that aspect.
Interlaken Ost is indeed much more "connected" with the main rail lines, as Annika notes. It does not have a lot of tourist attractons, but gives access to many ays to fill a few days in the Area.
The most important aspect of the weather issue is not the rain, per se, unless you are on your bike, but rather that in the Alps, clouds can obscure the views that you came to see from high altitudes. Paying to see the inside of a cloud is not a good use of money.
The timetable shows that the trip to IO from Wengen takes 51 minutes, of which 21 minutes is the trip from Lauterbrunnen out of the valley to IO. Grindelwald to IO takes 35 minutes.
IO to Bern is 53-54 minutes by frequent trains. Brienz is nearby, and a visit to Jobin or other wood carvers is a nice distraction.
For more perspective on the weather -
We were there for 2 or 3 weeks in June one year and had ain and clouds almost every day....except the day that we left. ;-)
On the other hand, even though I usually go in May, in 2014 schedule conflicts forced my trip to April.
In the middle of April, which normally has wetter weather more frequently than May, there was a stretch of about 10 days with dry, warm, sunny weather. On one day that was rainy was rainy, I got on the train, went 30 miles, and had sunshine.
I was able to get up on a ridge over Sumiswald at 700 meters elevation, in the Emmental not too far from Langnau, on approximately April 17th and take a series of pictures toward Trachselwald, Schloss Trachselwald, and the Alps, which I merged into the attached panorama in Photoshop.
The trees have flowers, but their leaves have not yet appeared. The fields are just beginning to green up. Snow on the fields was completely gone, but the Alps still had plenty of snow. In May, walking on the "Wanderwege" through the Emmental or riding the well marked bike trails can give wonderful views, especially if the farmers crop rotations have created a lot of fields of bright yellow "Rap" ( rapeseed in English).
The train from Luzen to Bern via Langnau that you mentioned passes through Trubschachen...about one stop from Langnau.
In Trubschachen, about 100 meters from the train station,there is a very old inn, dating back at least to the 1400's. I have attached a picture of the facade of the Gasthof Bären. The architecture is characteristic of the region. Also characteristic are family farms with multiple buildings, I have attached a picture of one on the road from Trubschachen to Mettlenalp, not far from Fankhaus.
On the ridge above, you can walk a road from Trubschachen along the crest, and look down on Trub, not far from Trubschachen.
Great hiking and cycling country....although a bit hilly. ;-)