walking from the hotels is possible, but not recomended as the majority of the roads are highways.
mass transit is available... but remember, the new meadowlands stadium is going to have a greater capacity than Giants Stadium did, and we all know what a mess that turned out to be trying to take the train out of there.
good news is that they've got a loooooong time to figure things out. they already put bus service back in for the Springsteen concerts at Giants Stadium, so that people could choose wether they wanted bus or train. of course there were 20,000 fewer people at Bruce... and the train lines flew. literally on the line and on the train in 10 minutes or less, compared to 2 hours at the U2 concerts.
whichever way you chose to get to the meadowlands... train, bus, drive, walk, taxi, car service... just be prepared for a long trip home.