I would say definitely try to make it to this plantation: http://fincavistahermosa.com/ They are a multiple Cup of Excellence winner and produce what I still consider to be one of the best beans Ive ever roasted/tasted! Also the last I heard they were very welcoming to visitors.
Heres my original post on the bean: http://coffeesnobs.com.au/YaBB.pl?num=1109816604
Java "Man does that bring back some memories!" phile