Dang this is a really tough question! There are just so many choices and too many options! And fishkeeping is really a personal thing. What a nice size tank to work with though, you are really in the drivers seat! Review your options and make a list of 3 - 5 Central American cichlids that you are intrigued with. Once I know what you are looking at it will be easier to help you build your tank around your favorites. I think that is the best way to go. I think you should start with juveniles, these fish will need to grow up together, this makes for much more peaceful tanks. It is really hard to get a bunch of adults throw them in a big tank and expect them to get along.
So pick your target fish first, then you add fish that they are most compatible with. Sometimes you can do a river location and do several species that are found together naturally, these makes nice tanks too.