Jean asked: What’s the position of bikes on the sidewalk ridden by adults?
Whether adult or not, bicyclists are allowed on sidewalks unless there is a local ordinance to the contrary. A bicyclist on the sidewalk must yield to pedestrians and make an audible notification when passing a pedestrian.
s. 316.2065 – Bicycle Regulations
(9) A person propelling a vehicle by human power upon and along a sidewalk, or across a roadway upon and along a crosswalk, has all the rights and duties applicable to a pedestrian under the same circumstances.
(10) A person propelling a bicycle upon and along a sidewalk, or across a roadway upon and along a crosswalk, shall yield the right-of-way to any pedestrian and shall give an audible signal before overtaking and passing such pedestrian.
In crosswalks, a probably not very well known provision of s. 316.130 applies:
“13. Pedestrians shall move, whenever practicable, upon the right half of crosswalks.”
The same would apply to a cyclist using a crosswalk.
In the US, of course, the custom is for oncoming individuals to pass each other on the right in supermarket aisles, airport concourses, building hallways, and on paths, walkways, and sidewalks. There would probably be little change in oncoming crosswalk users’ passing behavior if S. 316.130(13) were rescinded.
Pedestrians and cyclists who want to pass a slower same-direction sidewalk user will opportunistically pass on whichever side they deem most convenient, in my observation; no rule governs this, although a pedestrian who notices they are being overtaken may step toward one side to let the overtaker pass more easily. In any case, as Geo notes, a sidewalk rider is required to give way to any pedestrian.