You shouldn't hardcode any infrastructure specific things within your individual workflows ... instead, point infrastructure settings to Configuration Elements... then, within your workflow, choose the appropriate config element for the infrastructure that you're dealing with..
So as a simplified example, you could create 4 config elements, each with attributes defining clusters, gateways, datastores, etc... for the particular vCenter..
Next within your workflow, you should have some method of determining which vCenter you are dealing with, then based on that, you retrieve the appropriate configuration elements for that vCenter. So if you have a decision point that determines you are working with vCenter3, then load the vCenter3-datastoreclusters, VLANS, etc.. that are stored in the vCenter3 configuration element.
The above is a simplified explanation of one approach. Orchestrator provides you the flexibility and power to develop however you see fit. For more about configuration elements, see the following article:
http://blogs.vmware.com/orchestrator/2012/02/configuration-elements-revisited.html