There will be garages for more so just avoid those. You could also park in downtown which is just over the bridge from the stadium and on Sunday it will be $5 for all day.
There are people who pull carts with their bikes (not sure what they are called) but they charge about $15-$20 each way. You can either walk by the river on the river walk or just walk the streets which have sidewalks.
They generally only consider even days when there are fireworks or something happening at Heinz Field. Kristine, If you park at the casino it should be free on a Sunday.
