DaemonXI

I want to start working on an idea I've had for a while now. It's a social food website like Urbanspoon, but based around a university setting - focusing more on walking distance and specific location, and including ratings for, say, dining halls on campus.

I don't know where to begin with this. I have a list of features and ideas laid out, am working on designing the basic site layout on paper, and have no idea which programming language to start with.

Should I use PHP and MySQL since they're so prevalent? What about Ruby? Another one that strikes me is Python, but it doesn't seem to be much of a web language.