Yep, you can. It depends on the strain though, if its more on the indica side, I would probably wait another week unless you have height restrictions.
How do I tell what it is?
I have two of them, both bag seed from two different bags of weed.
One has slim fan leaves and has a nice smell to it already.
The other plant reminds me of a lettuce plant with big dumbo ear leaves and it has no odor, I assume it's a shitty plant because of the lack of smell?
I have some older pictures of the plant I want to flower in my gallery but it's grown a lot since then. It's actually grown like a motherfucker in the past 4 or 5 days, dunno why.