Really good map, and I think walking it is totally ok. Well, for me anyway: I do loads of things like that in Switzerland. I would have thought the stop for Bus 5 wasn't so far away. There's a bit of change coming for the buses in Geneva on December 13th 2020, by the way.
Only in Switzerland, looking at your pic out of the window above, would you get a bit of farmland in the city like that. Long may it last before it gets built on.