So I just updated to Express to use with my Forerunner 210 and I can't figure out how to only upload certain activities. I don't want to sync all the activities on my device as some of them are my husband's. Please tell me, I'm just missing the option.
Garmin Express does not contain the ability to Sync only certain activities on a device. You can use the manual upload method described in the FAQ: How do I manually upload data from USB devices to Garmin Connect? The activity file names are based on the date they were created.