As a owner of the Japanese version of ACNL, I wouldn't recommend getting both the software and the required hardware if you're only going to play just one game. Even though you get access to a few more holidays and receive different items from similar holidays, the game is essentially the same albeit struggling against language barrier if you didn't mastered Japanese. Yes, you'd be stuck with a system that will only support Japanese for the vast majority of the time. If you're going to get more Japanese exclusive games on the system and don't mind being restricted to one language, then go for it.
If you decide to not invest on a Japanese 3DS and a compatible copy of ACNL, you could always ask someone who do, get all of the items you need and be done with it. By the way, I'm one of the guys who own these things, even though I haven't mastered the language yet. I can even happily time travel to these holidays if you want to.