Don't worry about bike finding bike lanes. Cars are used to cyclists being everywhere in Manhattan except the highways on the edges. You can really just chill out and bike around. Take a side lane on the avenues--people are double parked in them every block anyway so cars don't drive in them unless the driver is an idiot. In that case, enjoy the frantic honking and go even slower. I actually pity drivers that honk at me because they don't realize that I'm going to be passing them at the next red light.