Also, JSYK: If you want two towns on one 3DS, you'd have to have either two physical copies or a physical copy and a digital copy. You can't have two digital towns.
Correction : you can but you risk game corruption and possibly having two wonky acnl games
"Risk" being that you probably will just end up with one or two corrupted files. Don't even bother with trying two digital copies, people get corruptions just from trying to get pictures off of their SD cards.