I ride in NYC and since you won't be keeping your bike out at night you are in good shape. I wouldn't go with drop bars to ride the city streets a lot as I prefer to be more upright to see city traffic. That doesn't mean a fully upright bike which is slow to me but rather a compromise - the upright but slightly aggressive geometry of a performance hybrid so you have some nice power still. Keep in mind I am a Steel is Real guy so I'd try to find a used steel hybrid with disc brakes, which are important as the city streets are dirty, so your braking won't suffer. $500 should find you something nice. A bike that was new for $1000 a few years ago can be had for well under $500 now and in good shape as well. Find some steel hybrid lines like Jamis Coda's or some of the Kona rides and I think Marin as well - and more and keep looking at Craigslist for them.
I'd also go with Pitlock skewers to protect your wheels, seatpost & headset. Once nice U-Lock will then be all you need to protect the frame. I keep my bike locked up while I go inside to eat somewhere all the time without much of a worry. You can lock on the street plenty if you are not in a terrible area of NYC, don't listen to folks who say never lock outside. Oh and I prefer 28's for my tires. Skinny enough for speed at high PSI and just wide enough to be ok on rough city streets. I waffled between 28's and 32's and 28's are just dandy to me. Others may find them a harsh ride YMMV