I'm not clear on the time / cost constraints. You're going back to the States, but want to find a EFL job in HK. You haven't got long before you go back, so you're looking for a short course. I'm missing something. Are you heading back to the States for a while regardless of whether you find a job here, or are you hoping that landing a teaching job could negate the need to go back?
The British Council no longer offers CELTA, and in any case this would be a minimum 1-month intensive study, just like the Trinity TESOL. You would also need to be on either a dependent visa or a study visa in order to take on a course like that.
The Trinity TESOL course is offered part-time and is possible to do on a work visa or dependent visa, however that's a 3-month stretch.
Not sure how well you have researched ACTDEC, but I'd be inclined not to stop at the University of Wikipedia. A Google search or two further turns up more information upon which to base your decision.
If all you're looking to do is find a basic EFL job that will provide a visa, then CELTA / Trinity TESOL may not be necessary, but from the variety of short, cheap, on-line alternatives, I really don't think it matters which one you choose.