I'd agree Koh Tao is a much nicer place, very laid back but with loads going on. And, er, if you can't pull in Koh Tao then you're probably cut out for a career as a circus freak
One of my favourite places, funnilyt enough!!! I went for four days and ended up staying for a month. You keep seeing people at the bars who told you 3 weeks ago they were getting the ferry next day, it's an easy place to stay. You can also turn up on spec without booking anything, all the dive centres have reps hassling you on the ferry. It's dirt cheap to stay if you can get a monthly deal somewhere. A word of warning, it's not easy to get around so you'll need to budget on hiring a moped, it's only a couple of quid a day but it all mounts up.
However, just because it's a nicer place it doesn't make working there any easier, you'll effectively be an unpaid volunteer bottle monkey and far worse if you do one of those internship thingies. Most of the divemasters I knew there were effectively working in exchange for free diving and weren't getting paid. They were also working feckin' long hours and being worked like dogs. Looking back, I think I was having a better lifestyle not working and paying for dives than they were working, probably didn't cost that much more. Full instructors seemed to make a bit of money but they seemed to be in a little closed cartel.
And if you do go to Koh Tao, the freediving courses that Monica Ganame runs are well worth the money (about £150). You'll learn more than divemastering! And don't miss the 80's nights in the Dragon Bar.
There are a few places in Florida that do some very good OW to OWSI deals and will arrange work placements on qualifying as an instructor that might be a better choice.
Cheers,
Stuart