old bay seasoning

Vadouvan curry

I would try whatever the people there told me they enjoyed. Maybe you'll discover some new fabulous way to season/cook your fish.

Recently made blackened cod with a blend of garlic powder, onion powder, salt, thyme and cayenne. It was to die for. I'm so jealous of the question-asker, that sounds like heaven. You should definitely do ceviche once or twice too :)

Salt and pepper, of course, and Herbs for Fish from Provence.

I'd go local. I'd go to the street market in whatever town you're in and look around. If nothing else it's a great excuse to spend some time in the market.

I'd try things like Epazote. Mexican oregano, Chile powders, cocoa cinnamo

Old bay is my go-to, but I like the suggestion of finding local items to use from a street market. Have fun!

Check out World Spice Merchants' selection of spice blends. Their Calico Fish Rub is delicious.

http://www.worldspice.com/blends/calico-fish-rub

White Miso Paste. Thin it out with some alcohol (like tequilla, rice wine or white wine) or water and smear it on fish and vegetable.

Local! Try achiote paste and lime juice, tomatillo salsa, local hot sauces, sea salt, pepper and lime. IMO no need to carry spices, instead bring some home...

try this recipe. It works well on grill. http://7th-taste.com/2011/09/11/vietnamese-style-pollock-with-ginger-liqueur/

I agree with SeattleJ-- go local. Use fresh herbs and citrus-- such great flavors to compliment seafood!
This is a great method for cooking seafood this way: http://and-here-we-are.blogspot.co.uk/2012/07/cooking-seafood-at-beach-easy-tidy-way.html

Basil, Bay Leaf, Cardamom, Cilantro, Allspice, Dill, Fennel, Garlic, Ginger, Paprika, Parsley, Rosemary, Sage and Thyme. Then there are all the spice/seasoning mixes: Tony Cs Creole, Chinese Five Spice, Herbes de Provence, Blackened Spice, etc.

Honey or Dijon mustard mixed with maple syrup. (yes, odd combo; really good on fish)
Penzey's Lamb Seasoning
Penzey's Northwoods (not the Fire one)
Fines Herbes Blend
Citrus blends or check an old Joy of Cooking for the citrus salad dressings, and also marinades.

Plus one for local. But it couldn't hurt to stow away a bottle of something just in case you can't get to the market that first day. Have fun! Mexican mercados are the BEST.

Try making this taco seasoning blend for mahi mahi tacos ahead of time. You can just mix the spices together and bring them in a jar. Pretty tasty.
http://www.epicurious.com/recipes/food/views/Grilled-Mahi-Mahi-Tacos-366731

If the fish is freshly caught, direct from the fishermen, then I always think that the simplest treatment is best. I like the way fish is prepared in Greece, and other Mediterranean countries - simply grilled, an olive oil and lemon dressing on the side, accompanied with some chopped red onions and parsley. No overpowering spices or condiments necessary.