Saturday morning downtown, the brick blocks off Main Street still in shade, and behind them a run of small yards that most people never see from the road. I. Lopez Landscaping Services does a lot of its best work in those tight spaces — a strip of grass between a fence and a garage, a front square the size of a rug, a bed under a bay window that wants weeding more than anything else. Small lots leave nowhere to hide, so the trimming has to be exact and the sweep-up complete. It is the kind of care that makes a two-family on a narrow street look as composed as anything up on the hill. From the center of New Rochelle out to the quieter blocks toward Mount Vernon, that is the work, week after week through the growing season.