I have had a lot of users come to me because the IOS 7 update caused issues with not all of their Google Calendars not showing up on their mobile devices. If for some reason no calendars or contacts are showing then you should delete your account and re-add.
To get started on your mobile device head to https://www.google.com/calendar/syncselect
You will have a list of your available calendars. Simply select the calendars that you want on your mobile device.
Close the calendar app.
Re-open the calendar and refresh the app by dragging down on the screen. It will take a few minutes for all of the calendars to show up.
As always let me know if you need anything!