"We go to bed too early."
Translation:Nós vamos para a cama muito cedo.
"pra" is basically super informal (almost slang) --although that's often what it sounds like when you hear it spoken. Proper usage (especially written) is "para a" (or, I believe, "à"). I've seen lots of comic books and Facebook comments that use "pra" though. It's kind of like "gonna" in English.
I was just about to ask the same thing and then I realized the most likely explanation. "Go to bed" is sort of idiomatic in English for "go to sleep". So to use bed in the Portuguese sentence it would literally be "go to the bed". Otherwise the way we use it would be more like "va dormir". That's my best guess anyway