Never gone with streetwalkers, so I obviously can't comment on prices and reliability.
But there was a sizable contingent of SWs on evenings in and near Oranienburg Strasse in Berlin, and they address you straight away, when they're not seizing you by the arm to begin haggling
![:D](https://www.ukpunting.com/Smileys/kolobok/biggrin.gif)
Hard to miss them, considering how they're clothed.
Calle de Montera in Madrid is also notorious for having SWs pretty much at every time of the day; I saw many even at noon when passersby and tourists are aplenty.
As Marmalade said, Geneva has a neighbourhood near the station (Paquis area) which is the main SW area - and some salons / massage parlours as well. As said, seems active day and night. Though there's a slow creeping gentrification of the place and I wouldn't be surprised if all that changes considerably in the next 20 years.
Lausanne has a quite limited and very localized scene, officially sanctioned - area has been massively reduced a couple of years ago. Not sure how much SW activity you would find during day time.
Since we're talking Switzerland, if you have a car, Zurich also has a drive-in system with sex boxes, which replaced part of the streetwalking activities.