I can suggest the following options to migrate the VM from local to SAN:
NOTE: Make sure you have a full VM backup before you perform the migrations and its recommended that you do this after business hours.
1. If you can upgrade to vSphere 5.1 it has an option where the VMs can be migrated to a new ESXi host & Datastore, refer to the documentation for vSphere 5.1 and topic "Migration with vMotion in Environments Without Shared Storage".
2. Use VMware Converter to clone the VMs
3. Use vmkfstools -i command to clone the VM disks, refer to VMware KB 1000936 & 900 for more information.
Options 1 is easy and Option 2 is the safest because your data on the source remains intact.