Segment, segment, segment is almost always the rule to follow. Unless you have a specific reason to do otherwise, place each office on its own VLAN, though using the same SSID is acceptable since that will allow for easy roaming. If possible, configure L3 links between the sites.
If you're using lightweight, I believe that you cannot use the same SSID with a different VLAN, assuming the APs are all on the same controller.
Hopefully this is what you were looking for. Let me know if it's not!