I'm going back to China this week too, been almost 2 years. Unfortunately, no bike for me to ride while I'm there

You're Garmin is probably going to have an offset.

ShuBen is right, Locus is the way to go. Been using it for a year now and love it. Hands down the most amazing GPS app available. Not something you're going to learn in a day before heading out on a trip.

Enjoy your trip.