John:
You can probably just send a letter addressed to Trish Carter, San Pedro, Ambergris Caye, Belize, Central America.
As far as Jim Wade, I'm not sure that he picks up any mail at the post office, but probably since the Pier Lounge sees him once a week, they wouldn't mind if you sent it to Jim Wade in care of Pier Lounge at the same address above. I hope you can get in touch with them. I know they would both love to hear from you.