That's definitely the best attitude to go in with, because:
1) everyone hates that whiny kid who's gotten into a bunch of schools and is complaining that his dream school hasn't accepted him. When it's March, and everyone is stressed is hell about getting in at all, and someone is complaining about how he got UCSD but not UCSF, or he got into a school OOS but nothing close to mommy and daddy, you'll see. Everyone hates that kid. Rightfully so.
2) There are few things as uncertain as this process. If you think you're the perfect fit for a school, you may very well be wrong, or the adcoms might disagree, or the school might be looking for a different kind of people, or you may have overestimated yourself. Either way, if you hang all your hopes on the school that's the "best fit" for you, you'll probably be disappointed (commence annoying whining).
3) Pretty much all schools are the same, except for some minor differences. Waxing poetic about one just makes you look like an idiot to the students who are in med school already and know for a fact how ridiculous you sound.
4) Perhaps most upsettingly, having a first choice school before you even interview makes you blind to the virtues of other schools. If you get an interview there, you're biased to think everything is perfect and lovely even when it really isn't, and you don't have an objective mindset when checking out other med schools that may very well be a better fit for you. Every year you'll see people who end up having to go to a school that wasn't their first choice, who come back and say they had been totally biased at the interview and that they actually ended up somewhere they love. And you'll see people who'll painfully regret their choice in med school when they realize they hadn't really grasped the school at all when they had declared it the perfect place. This is really depressing.
So yeah, don't have a first choice school, especially before you interview. After the interview, you'll probably have a basic ranking in your mind, but try to stay as open-minded as possible until you get your acceptances. Then you can be as picky as you want. But for now, do yourself and everyone around you a favor, and don't fall in love with some school's website or ranking.
