In most destination type places I have been, Instructors were hired over divemasters almost invariably as an Instructor can (and quite a few prefer to) do the job of a Divemaster, but not the other way around. On the liveaboards I worked, the DM certified crew were EXCLUSIVELY local talent with tons of experience, while the expatriate crew were ALWAYS Instructors (with one exception of a Captain wo trained as a DM after getting the Captain job
)
If they want to travel then the opportunities break down like this: you can volunteer as a DM in many places, but in order to make your vacation 'break even' you will almost invariably be required to sell/teach. As AMERICANS (rather than local Caribbean, Thai, Mexican, etc nationals) working abroad, the number of PAID DM positions will be VERY limited. Most places treat expat DM's as interns who are just learning the ropes on the road to becoming Instructors.
The "locals", however, are quite often considered serious as DM's. In my humble estimation that has much to do with the often "considerable" expense to becoming an instructor: When their father made less than 2$ a day, and now as a DM the Diveshop pays 20$ a day that is great money. Quite often they can earn their way through the DM program fees through schlepping tanks and scrubbing boats, but the PADI fees for the instructor exam are like 400$, the books another 400$... and you have to have a Course Director and/or IDC involved; all hard currency expenses that serve as a massive impediment to these 20$/day employees who are sending 18$/day home to support their (extended) families.
So basically, locals CAN make decent $$$ as DM's when the $$$ earned is in context of local economic conditions. If you are wanting to travel, live and dive, Instructor is really the ONLY option for expatriates to tour the destinations and have a social life, live in somewhat acceptable conditions and break even financially.
