You could last year - though you dont pay at the turnstyle but need to go to a ticket office - I think they have a seperate one for away fans Hopefully the club will clarify on the official site once they stop selling tickets or Call the Derby box office
I would get there very early if you want to pay on the day, you have to go to the box office (just the one for home and away fans) and there's likely to be a long queue. A couple of years ago I was at the back of the queue 5 mins before kick off and it was going nowhere, when some guy offered me a 'complimentary' ticket for a fiver, so I took him up on it, I had to sit with all the Derby idiots, but it was worth it to see us hammer them.