If you have VMware Tools installed on the VM and are on vSphere 5.0 or later, you can use the GuestOperations object in the API to run scripts and programs in the GuestOS without network connectivity:
You do still need credentials in the GuestOS (no one wants to have their GuestOS security bypassed!). But usually the simplest approach is to create a service account in your template image, use that for the GuestOperations calls. Then if you can optionally to delete that account in your scripts/programs.
You can also do a lot of those settings during the clone operation with a reconfiguration spec. So depending on your network configuration needs (for example if it's fairly straightforward), then you can configure it during the cloning operation.