I'm a 21 year old software engineer, so I guess I'm in a similar situation as well. I make quite a bit more than $2400 a month, though.
I'd say save up for a good sized deposit (try to be a little patient and you might be able to wait for the STI version if your interested
) before you commit to a long finance option. I would've if I could've waited - I keep kicking myself for not waiting for the manual transmission though (although the AT is very fun still).
If your in a stable job and feel you can afford it, I say go for it. You sound smart enough to be able to make an excel spreadsheet with all your bills & figure it out - also keep in mind emergencies. I use mint.com for my finances, maybe that could help you?
EDIT: Oh, and to go on what the guy above me said - cancel your cable bill if you have that crap. Netflix is about 10% of the price. Also look at no contract cheap phone plans (boost/metropcs). Although, I gotta say if you
need to cut pennies like that you really shouldn't buy the car.