A couple of things.
First, if you're going to China, work full-time if you can. Work experience will give you far more than just studying in the classroom, even if you're in China.
Secondly, you're not going from basic to fluent in one year. You can certainly learn a lot, but it's not going to happen. Think about how much trouble non-native English speakers have going from broken English to a level that allows them to discuss case studies at b-school. It's not a year's work. It's more like 3-5 years work at a minimum - the older you are, the longer it takes, and you're no longer a child or teenager. Moreover, you're going there for a year, only to go to a US or Euro b-school where you'll be mostly speaking English, which will mean no matter how hard you try, your Mandarin will regress to some degree.
And finally, b-schools are looking for individuals who have the potential to manage large numbers of people, not large numbers of money or "things". It's about managing people. If you aren't able to convince the adcoms that you're as good with people as you are with numbers, you're going to have a tough time getting in, especially at the top 16 programs.
If you want to master Mandarin, go for it, but it's not going to happen overnight. And do it if you feel it's best for you, irrespective of your b-school plans - don't let "bschool adcoms" dictate what you should or shouldn't be doing.
Follow me on Facebook