You're asking in the right place-I'm a Reno cab driver on the weekends. You don't have to call one-it's legal to hail off the street here-but except around the casinos, the only way to realistically get one is by calling. There's usually a 2-4 of them meeting both trains, even if they're late, though sometimes there's not enough for everyone. If there aren't any the Harrah's cab stand is half a block south on Center Street, and there's usually at least two waiting there. Which hotel are you staying in?
Edit: There's not an actual stand per se at the station, cabs have to loiter on Commercial Row outside the station, which limits the amount that can sit there for any length of time.