Does duolingo track time you've spent on each language?
I want to know because quite a few sites say that to reach proficiency in a language, I'll use spanish since I am learning it, it takes 575-600 hours. I want to see how far I am along to that time.
No, Duo only tracks how many lessons you've done and how many XP you have earned.
Those sites that say you need 575-600 hours are good as far as setting some kind of expectation, but they're also bad because they don't say HOW those hours could be most effectively spent. Flashcards? Duo lessons? Time in a classroom? One on one with a private tutor?
To make the most effective use of your time, I'd recommend mixing new lessons with reviews in Duolingo, doing a flashcard program like ANKI or Memrise, and doing some reading and listening practice with news articles, YouTube videos, etc. Finding some music you like, learning (and translating) the words, and singing along is a good way to get your mouth used to making new sound combinations.
There are a lot of additional language-learning resources on the Unofficial (but still Awesome) Dulingo Wiki: http://duolingo.wikia.com/wiki/Language_resources
Hello, the nice giraffe already gave a very good answer to this, I'd just like to add this nice illustration of the 'mountain of language learning': http://www.bitesizedlanguages.com/app/webroot/attachments/2013/04/language-mountain.jpg and say that Duolingo is aimed at levels A1-A2.
Also, the other day I was thinking the same and decided to do some rough estimates: Looking at my XP I can see how many times I have practiced. For me, I have 3110 XP in German, so I went trough 311 learning sessions. I spend on average 3~4 minutes per session, so I estimate I spent between 15 and 21 hours on Duolingo already. Not very precise, but it satisfies my curiosity