If you have one, certainly bring it. My wife made me get a phone after I was an hour late due to flats. I have a Virgin Mobile phone so it only costs me $5/month, given the level I use it at.

Personally I'd skip it, I'm OK with walking home in the rare case that I have something critical fail, but it makes my wife feel better.

Cell only isn't an option here; there's barely any coverage at my house.