i live on the ues, it's not that hard. I don't understand why bike commuters will only commute in bike lanes. half the time cars don't respect them anyways. FYI, the bike lane resumes on 1st avenue at 72nd street and runs all the way up to 125th street. the bigger issue is the crappy concrete that is first ave as opposed to asphalt. if you are riding 23mm tires you have to bevery careful that you don't get stuck in a crack in the concrete.
BTW, if your coming up first ave and there is no bike line, use the dedicated bus lane on the right side of the ave. cars will get ticketed for driving in it and there aren't that many buses in it