My girlfriend and I like going to El Pollo Loco because their meals are pretty good and decently priced. But the last few times going, the customer service has been absolutely horrible.
I get the drive thru you can't really hear, but you don't have to be rude. Also don't rush the customers when they order, sometimes it's hard to decide what you want. It's been common in a lot of fast food places and even restaurants lately of employees giving rude customer service. Trust me I work on food as well, but I could never be rude.