Yes. In fact we strongly recommend that you only sync the data that each user need at any given time. Maybe that is "my customers" or "my customers to visit this week" but filtering the sync is key to a good user experience.
(If you're interested in reading more on this, check this out: What we learned making mobile apps.)
Filtering records this way is built into GoZync, the sync engine behind GoMaps. For instructions on how to add these sync filters to GoZync, read this: Downloading Found Sets