20 had pretty good numbers of antelope last year and I saw several nice bucks on what little public there is. Granted this was a week before the season. But like several have mentioned, there isn't much land you can access to hunt, and what there is gets hammered pretty bad the first few days. If you really must hunt that unit I'd plan on going later in the season when everyone is gone, you may not find any big bucks but you should still have a fun hunt.
By the way, the biggest antelope buck I've ever seen alive was in 20. This was in 2009, towards the south end of the unit on a small section of public. This lone buck maybe 100 yards off the freeway just feeding on some sagebrush, he was easy 17" with lots of mass and great cutters, just a brute. Most of the bucks in that area tend to be shorter with good mass, not lots of tall ones but you do see a few. Good luck on your hunt.