Hmmm...20L...cleverly marked with a big "20L" at the end, some nice yellow chevrons to tell you to stay out of the overrun, and...well, that's about it. I guess if he was watching toward the middle and didn't pay attention to the end, the taxiways could look pretty similar.
Not a great layout, though; looks like all the commercial terminals are on the east and about 2/3 of the GA on the west, with the big runway (20R/2L) on the west side and the little one on the east, so everybody's having to cross everything most of the time.