I secod what
leonardoperezsalles said. FPL's are usually required by law.
Also VFR between sunset and sunrise is usually forbidden in most Latin American countries.
The International Flight Information Manual (IFIM) contains useful information, especially with respect to requirements.
International Flight Information Manual (IFIM)
AOPA can also be a useful source of info, if you are a member.
Old WACs/ONC's combined with current IFR Pubs (enroute charts, aerodrome charts with frequencies) will provide you the info you need to navigate your way down there.