There is no easy fix on this: Marketo is not good at comparing numbers and telling which ons is the higher. So at the end of the day, part of the process will have to be done in your CRM (specifically deciding to which sales the lead should be assigned).
Nevertheless, the fact that you assign the lead to one sales does not necessarily means the other sales cannot give a look to it: it in fact depends on the security model set in your CRM. You will have to set strict SLA rules to make sure that the sales know they should qualify a lead in a short timeframe so that if it is not retained by the first sales, it can be assigned to the second one.
Second thought: you are talking here about regional scores. Have you thought about cross checking the lead scores with address info and assign the lead more based on the address than from the highest score? The issue would be harder if you had set a score by product line.