If you can’t find a wedding planner in the States who has experience working at the destination and who doesn’t speak the language you should search for a planner at the destination. Someone who also speaks English. You have to be able to communicate clearly with the planner and vendors.
The Internet of course is a great search tool but just because a planner shows up #1 in a Google search doesn't mean they’re the right planner for you. If you’ve decided on a venue ask them for recommendations.
You may also want to look online and in magazines for destination weddings in your area and if there is a credit for a planner search them out. Another great resource is Destination Weddings & Honeymoons magazine. They should have both real weddings from around the world and advertisements for planners you can research.
And if you do hire a planner in the States know that you will have to cover their travel costs to the destination and accommodations, so get all of their costs and responsibilities in writing.