This photo needs cropping. You have the horizon in the middle of the shot. You do not need all that beach if the subject is the sky. You could also crop down some of the clouds less is always more.

It is not the purchase that is of value it is the after service that is. Buy from a American USA based company. I use The Photo Center in Brick NJ. They supply excellent after purchase support, and if there is an issue with a used lens they will make it right.
I don't trust that after purchase service from outside the US is reliable. Perhaps you are able to return the defective item, check out what it costs to send a lens back to Japan. Buy USA support the merchants here.

Tamron's new lens , i think it is 18-400 or 16-400 is a great walk around lens. This has all the features you need and is reasonable cost. My friend has it on his Nikon and there is no barrel distortion and it is sharp through the entire zoom .
Dont buy anything until you check out this lens.

I agree, but would cut 80% off the bottom.

They used to do that in NYC also...until they got caught and had to pay all the taxes after the audit.

So it seems that almost every locality has a favorite photo store. I support "The Photo Store" in Brick New Jersey.
I check prices on the internet first and in every case the store is the same or less. One instance they quoted higher and when I showed them the online price they reduced theirs to meet it.
The local store is able to give you personal service that the online stores can't give you. Support your local store, if they don't give you the service you expect then call them out, let them know you expect more from them to keep you as a customer.

Some times you need to micro adjust for that lens.

The 100-400 is a nice lens but the 16-400 is just as sharp, and small enough to use as a walk around.

Bag will stop the condensation from evaporating. No bag, just let it warm up. You could also take some shots with the condensate on the lens, might give an artistic look.

Fkaufman I was being sarcastic.

If you want the locals to laugh at you bring the nets. Rich, if you are with a tour the guides make sure you are not put in harms way. There are also Caymans along the rivers and canals, I guess you should bring steel shoes also :)) Mosquitos, yes they are there, perhaps you should take malaria pills also. Oh, and don't look up at the monkeys, some of them (howlers) will pee on you. The frogs some are poison us. People make it sound so dangerous, perhaps you should stay home in a bubble?? I have been 3 times to Costa Rica, it is friendly to Americans, most speak English and they accept the US dollar everywhere. Last but not least the places you are visiting are beautiful each in their own way. Enjoy, don't overthink the trip. Take many pictures.

Take bug spray. I would imagine in a hotel that is air conditioned bugs will not be an issue, but if you are out in the rain forest especially dusk, bugs will be an issue. Take plastic bags as well just in case it starts to rain in the forest:). I did not need a tripod except on Volcano Arenal for night shots of the hot rocks. Not aware of a tick problem but I did wear long pants and shirts with sleeves with bug spray as a precaution when trekking the rain forest.

Nice snapshots. They would be better if you had at least one whole flower in the shots.

I tend to agree with you, but if you are entering a juried show you need to fill the frame and remove distracting objects. For example your shot has a twig coming off the main branch that leads your eye off to the corner and out of the picture. It is the second thing you see and becomes distracting. The photo has more impact with the twig cropped out.

This is a good walk around lens. F8 is the sweet spot.
Shooting Raw you are able to sharpen the photos a bit.