Yes you can. You should check for the number of employees on each location to determine which one needs more than, second and so on and start subnetting from that point forward.
The thing is you would not do 192.168.1.0 /27 and then /28. You would do /27, and then starting from the last IP address you use you would do /28. Later I will explain more if you need. Right now I have to leave.
Edit: So you if you subnet using /27 you would have a range of IPs going from 192.168.1.0 to 192.168.1.64. That would be your first subnet. After that you would can subnet again using 192.168.1.65/28 which would range until 192.169.1.96. If that fits your needs you can remain with /28 or if you need smaller sub networks you can use /29 after that and so on.
Hope this helps you.