This is what I know . . . .
Here in Mexico, there are some ports where Tuna boats "park" Ensenada, La Paz, and Mazatlan, there are lots of tuna boats at these places, I know pilots who have been there, and know a few things about them. But first of all let me say, getting an FAA ticket goes further with these people, and having those 200 hours will certainly help, actually I know of 2 guys, one spanish and one american who got hired with a little more than 180 R22 hours, if you get those hours get them in the R22, tuna boats seem to have many of these and will certainly appreciate them. (although I think the 300 is a much better helicopter, I really feel uncomfortable on the R22's, sorry)
My spanish friend got hired in San Diego on the US side, he worked on a Mexican ship with an FAA license, got hired with 190 hours and got about 8hrs. instruction before leaving with the ship, he called all the tuna operators 1000's of times and they always said they needed more time, then one day, got in tight spot and someone called him.
The pay is OK you make on a good trip (2 1/2 months average) about 6,000.00 USD which is ok for a a beginner and considering you don't spend while on the boat?
Tuna boats operate in Mexico, Panama, Venezuela all spanish speaking, spanish will definately help, (almost a must I would say)
I know one guy who spotted in Guam and he only said "it was the worst experience of my life" so beware with this Guam place.
Most ships I have seen in Mexico look pretty decent to me, helicopters are also good, its a dangerous job for a beginner, I have a friend who caught some net TO in a 206 and ended up in the water, helicopter sank, then about 5 years ago, there was this pilot who left on a boat, the entire boat dissapeared and NOTHING was found ever of the ship and its occupants.
I also have a good friend of mine who is 52 years old and every year he eagerly awaits the time for his yearly fishing trip, he says its the best time in his life when he's on the boat, and he always brings back pictures that make me want to go just for the excellent experience.
Don't tell any prospective employers you are there to build time and leave, try to make a commitment with them for say 1 year of trips, they will love that and consider making you a pilot.
I hope I haven't confused you further.