Fucking Hard, to answer your question. It's different from Europe because Khanji aren't letters we're used too. I lived in Europe for two years and was able to figure things out, plus you learn a good travelers sense and build experience and instinct. That won't matter in Japan.
Tokyo is ok, it's a tourist city so it panders to English people a bit. I only visited for just over a week, for my brother's wedding. He, and many of his friends, explored with me and translated and I had a blast.
It's totally worth any headaches you might get from getting lost. But just keep in mind, you can't work through a sign like you could in Europe (hoping that one semester of Latin pays off).