Bring 7$ in coins, then you don't have to queue for the ticket! You can get it from the machine on the bus.

However, my ticket didn't work properly. It was accepted for 24 hours on buses, but at the metro stations it only worked sometimes, most of the time it wouldn't. I had to walk up to the counter several times and explain what kind of ticket it was to be left through. Sometimes I was treated rudely, like if I was trying to pull of a scam or something. The people there asked their supervisors, once they even called someone and I had to wait a few minutes before they left me in. A nuisance.