Wherever they happen to be when the urge strikes (nude) (incontinence)

... Pretty much anywhere, as if they were babies with no diaper on.

There will be no peeing in toilets, so it will be normal to just let go automatically, while doing anything really. If you hesitate, you will be perceived as having a medical problem. Of course there will still be toilets, it's just that those are for number two and if you try to use them for pee, you'll find they aren't designed to catch human urine, and that people might regard this as hogging the toilets.

You will also find you have no bottoms. This is because in this world, people don't wear them, or else they will get wet. In fact they will typically go around nude unless the weather or some other condition calls for it. If you must wear bottoms for whatever reason, they will be waterproof and easy clean in case you get pee on them. And you'll have a diaper on underneath.