Alice, the lubbers aren't full size yet, mine are still black in color and only about 4-5 centimeters long, so they're not always easy to find. Lubbers seem to have good eyesight, and when they see you will move behind a leaf to hide. Best time to look for is the last couple hours of daylight and mid morning. If it is lubbers nibbling on your plants, keep looking in the area where fresh nibbles are.
I read somewhere the female lays eggs where she was hatched, so I went to the spot I start seeing the nymphs in late Feb, early March. Last year, I found them not even on my property but my next door neighbor's yard in some unkept grassy area with weeds, and again this year the same place. I sprayed them with ant and roach spray, and it killed them pretty quickly, got a good 60+ at one time. I have been battling them for well over 7 years, but the last two not near the amount I had been getting.