I usually didn't either, but the (tedious) technique I used led to a lot more text in my dreams. I think because my subconscious was looking for them.

You have to spend a few weeks making this a habit: Every time you see a sign read it, look away, look back, and read it again. Once you've done that awake long enough it'll become a proper habit and it will carry through in to dreams. And in a dream when you look back the sign will be different - which will make you realize you're in a dream.