Glacier bus from Sogndal on May?

There is no bus to the Jostedal Glacier in may, only runs from mid June, sorry. But there is a bus to Solvorn from where the ferry to Urnes run: Bus to Solvorn ferry: Urnes ferry Timetables for May is not set yet, but don't expect to many changes. If going on a tour on the Jostedal Glacier you need to hire a car for the day.

If set on going to a glacier, Bøyum Glacier and the Glacier museum at Fjærland might be an option, not the same by far I know. From Fjærland you could go by ferry to Balestrand and Bergen Bus Sogndal-Fjærland, the Glacier Bus will leave the museum at Fjærland at 14:35 and take you to the Glacier and to the ferry at Mundal leaving for Balestrand at 15:20 connecting with the ferry to Bergen Fjærland info

Have travelled the area a lot by car, not by bus myself though

I only stayed in the area for a week last year but I would totally recommend staying in Solvorn over Sogndal. A little town yes but incredible scenery, beautiful houses, great hiking & right at the doorstep for ferry to Urnes. Sogndal is a little (sorry!) dull and I wouldn't go all the way to Norway to stay there. If you stay in Solvorn, you should try Eplet b&b - you can google it - as a great base for exploring the region & nearby glaciers, as well as a very comfy & cheery place to stay. The owner Trond Henrik is a fantastic source of info for coordinating buses, boats, etc in the off & low seasons and helped me work out everything via email really quickly. Sounds like i work on commission but in actual fact just can't recommend his help enough - the timetables in that area are pretty wacky to me!!