If you are interested in mestizo-style ayahuasca ceremonies in Peru, I can recommend Ron Wheelock. He is a gringo, but good... he has such a reputation now that he sometimes has native Peruvians come to him for their first ceremony. It's nice to be able to work with someone who speaks english as a first language (or at all for that matter) and without the usual cultural barriers—in that sense, he is able to act as a bridge between Westerners and the Peruvian milieu.
Regarding sapo, you might do well to get in touch with Peter Gorman, he's on the aya forums as pgorman. He's something of the resident authority on it.