bz isnt insane at all, just a different than here. go with the flow, and keep expectations at home, and you will be fine.
i suggest u book the earlier flight. tropic's standard MO is if you miss the earlier one, due to any reason, they will just plunk you on the next. the tropic flight is never a worry...they always get u there. once you land at international, the rest goes smoothly.
I am with Peter on this one, as I have seen them go both ways at Goldson before. One time I saw them holding the Taca flight going south, because Miss Belize was running late (she came running into the airport as you heard the jet screaming down the runway, very upset)and another time a person that I know first hand was denied boarding going to the US, because she arrived at the airport counter an hour and fifteen minutes before her flight (took longer than normal to get bags off the puddle jumper) and by the time they got through the line it was under an hour.
I have walked up to the counter twenty minutes before a flight to the US and gotten on, so it is a total crap shoot and I guess that it just depends on which way the wind is blowing.
As far as tropic (this was a couple years ago before fuel skyrocketed), I have seen them pullout another small plane and send it out if they were overbooked on the caravan (generally a much smaller Cessna 172 or the like, I know I was on it to Goldson)
But there's a world of difference between being booked on a flight and missing through no fault of your own, and deliberately choosing to go later. Tropic really do bend over backwards to help, but at the end of the day they do have to make a profit.
I'll just add here that this conversation only applies to Tropic. With Maya you have no idea when you'll get there, if at all.
I would go for the 2.5 hours. Several years ago, we were late leaving San Pedro which caused us to arrive at Goldson one hour and forty minutes before our flight departed. The security and Continental personnel bumped us off our flight. Thankfully, we had been scheduled on Continental's early flight and there were seats on the afternoon flight. When I schedule guests' flights out, I always err on the side of more time. If they insist on taking a later flight, I explain the possibilities and do what they ask.