Contrary to what many had thought, it turns out that Wrocław will have a World Cup 2018 fanzone. A private company are currently constructing one at Hala Stulecia.
According to Gazeta Wrocławska, the fanzone area will be big enough to accomodate 300 people. However the screen may well be visible from outwith the fanzone area, so in theory the number of people who gather to see the big games could be even higher than that.
The fanzone organisers state that they will show every game (presumably with the exception of when group games take place at the same time).
People will be able to enter with food and drinks purchased at the nearby 'emotional zone', however bringing your own booze to the fanzone will not be allowed.