I've traveled around most Central American countries over the past few years on surf trips and have tried pretty much all the local beers in each country I've visited. Right now I am in Panama and the beers here, like in other Central American countries, are all the same American-style pale light lagers. I have not found much difference among the varieties of beer, as it's all pretty bland.
That said, one thing I do when I am in a place where I question the beer quality, is to stick to whatever brand is offered in brown bottles. The reason for this is that people transporting or storing the beer might not be so careful to keep it out of the sunlight. If beer ends up sitting in sunlight for too long, bottle color can actually have a huge affect on its freshness and quality .
Why does beer get that "skunked" taste when its been exposed to light? Hops! When hops are boiled during the beer-making process, they release alpha acids. When alpha acids are exposed to sunlight they produce some of the same chemicals that are contained in skunk spray. It's not what you want in your beer! Green bottles allow green and blue light to pass through, giving the beer very little protection, while brown bottles are actually successful in blocking it. Clear bottles are the worst as they do not do anything to protect your beer.
This is not to say all beer in green or clear bottles are bad. First, beers that have very little or no hops will not be a problem. Also if beers are well cared for when they are transported and stored, they will also be just fine. But in Central America, or any other place where you may think beer might be sitting out in the sun, go for the beer in the brown bottle.
I have sampled all three of the local macro-brews here in Panama (above photo), which cost about 30 cents each at the super mercado. Sure enough, the very first green-bottled Panama beer tasted a little skunky to me. The other two, Balboa and Atlas are pretty much the same as a Budweiser or Coors in the States.
Other Central American beers that I have had while on surf trips are Victoria, Toña, and Premium (clear bottle, and easily the worst) from Nicaragua, and Imperial and Pilsen from Costa Rica. They are all pale American-style industrial lagers and are more or less exactly the same from one to another. I would also recommend staying away from any imports--while it might be tempting, it's usually more expensive and the quality has most likely diminished due to long travel time.
So I'll be sticking to the brown bottled local macro-brews for the rest of the trip (unless I get lucky in Panama City). They seem to taste then they are when I am at the beach and they are ridiculously cheap. Otherwise I'll be working on my rum cocktails.