Great point Thalassamania brings up about the agency related to teaching style. However, forward think this one through and think about where you want to work and the agency they represent.
The majority of posts, so far, is to take your time and that is the best advice. However, if you decide to take a different quicker route with a total immersion program “Pun Intended” think about the agency where you are expecting to teach. Example. The Fiji program might be a NAUI instructor program and all of the California shops might be PADI. Make sure you align your training where you ultimately want to teach.
From my experience, I took AOW, Rescue and Dive Master through my local shop along with gear purchases. Because they did not have a course directory they wanted me to take the Instructor Development Course at their affiliate shop about 90 minutes away. I decided to take the course in warm Florida in November. When I came back to the shop with my OWSI card they completely black balled me and stated because I was not taught by them (affiliate shop) then I could not teach at their shop. My point is think about the big picture. Set a goal and plan the path to that goal!
LDS often may do this with an instructor that they did not personally bring up the ranks. Its a business decision usually. If they trained you then they know your personality and abilities.Being that a new instructor has no proven history this is the only way that many LDS feel and I can understand that.
Very often once a new instructor HAS experience and is known in the local industry a LDS May be more willing to take them on as a instructor.
Here in NY I have worked at/taught at quite a few of the LDS in the area and can usually get a class atdifferent LDS's fairly easily.
So what I suggest to do is take the courses at a facility that you think you may wish to teach at, or at the very least in the geographic area you wish to teach at. If you go the other route get experience teaching in the local area and make aname for yourself. Become known in the local community, get your face seen at dive sites and boats with students, then see if the LDS is willing to give you classes. Look at it their way, you are a LDS and have an opening for an instructor.There are multiple instructor's trying for the position.Who will you give the shot at?? Someone who displayed a willingness to be a team player and did their training with you or someone with no past experience and who went elsewhere and left them out of the picture?.