Don't worry about trying to walk around Buffalo. It isn't really a walkable city because there's not really anything to see. The truth is that it's a dirty, old, embarrassing city with almost nothing to see. Just focus on the game and make sure you go to the Falls and do Maid of the Mist and Cave of the Winds and it'll be a good time. If you want to go somewhere in Buffalo, you could walk around the waterfront, but it's not anything to write home about.
Game / Niagara Falls / food. I recommend Wingnutz and Bar-Bill for wings. La Nova or Bocce for pizza.
Beef on weck isn't anything special at all; don't feel obligated to try it. It's just a roast beef sandwich.