Business Rules: routing ticket by location of user

Our current routing system for our company goes like this:

Ticket entered into SD+ ->
Basic Triage by Service Desk Personnel ->
Manual routing by Service Desk Tech to Proper Site Queue ->
Site Tech Triage/Support and possible closure ->
Possible Routing back to Tier 3 Server/Desktop support for enterprise issues. -> Incident Closure

Our company routes calls for service based upon the location for preliminary triage. For example: Users in Los Angeles will submit tickets that should be routed to LA helpdesk support.
Users in San Antonio will submit tickets that should be routed to SA helpdesk support, so on and so forth.

At any rate, we haven't found a way with SD+ yet to be able to route on user location

Fixing this keeps our service desk from having to re-route 40-50 tickets per day.

I've submitted this to the programmers as a functionality request, but don't see it being filled anytime soon. Any help or advice would be wonderful.

Thank you in advance!
-Larry