You can usually find Atalanta at the bottom of Serie A or the top of Serie B. It's a good place to enjoy the irrational passion that is football, and it's as good a provincial Italian cultural experience as anything else.
The atmosphere is good, especially from the always-packed Curva Nord side of the ground.
Cheapest tickets are 6 euro. The obvious ticket windows aren't usually open any more. Go to the south side and they are probably selling tickets from an office through a window. You have to have ID for each ticket you buy. Curva Sud or Parterre would be my recommendation, Curva Nord if you are feeling brave. Tickets for children(and women!) are half price for all areas except the Curvas.
People living in and around Bergamo - especially in the valleys - have a common venue once every fortnight. They gather at the Stadium to watch their beloved team - Atalanta BC. They are one of the hottest supporters in Italy, sometimes known for being violent, but most of the time cheerful and very stuck to their black and blue striped heroes. Watching a football match in Bergamo can be an entertaining experience, even though the team is now playing in first division (Serie B). Not less than 15,000 attendance.
Equipment: Wearing an Atalanta scarf would improve your sympathy towards the local tifosi (supporters). You can get it just outside the stadium.
Cycling is not so common in Bergamo being a hilly city, but the lower city still is rather flat and outside the major streets it is pretty OK to cycle.
Atalanta play soccer in Bergamo, they are currently in serie A - the highest league in Italy. Did not manage to see a game, but here's the stadium anyway!