Yes, you can use the other servers.
The simple way is to change your SIP Server and/or Outbound Proxy to a different server.
us.voxalot.com
au.voxalot.com
eu.voxalot.com
See a typical set-up in the Wiki
Setting up Linksys PAP2 - Voxalot FAQ
Please also match the preferred cluster in your log-in page to the selected server.