Oh gosh, 1.5 years? I took 3 months off from the gym this summer for triathlon training. Started lifting again this fall. I remember after my first session (tried to take it easy), I could barely lift anything for 3 days. My biceps have never been so sore (they looked like they had retained their tone . . .)
Take it easy, that's a while to have been not lifting. By starting now, you'll be moved up to the higher weights by the new year. While all the resolutionists are fighting over the 5-10 pounders, you'll get your choice of dumbells at the gym.
The best part about going up hills is riding back down!