I wouldn't even touch this as you and I could have the SAME package sent to us from the SAME person, SAME markings (just different names) and have 2 TOTALLY different experiences!!
With that said - the MOST POSITIVE stories I'm hearing are from people having things sent to them at their regular Costa Rica PO Box.
Another hint I got for packages sent via Federal Express is as SOON as you have the AirBill number - IMMEDIATELY CALL Federal Express in Costa Rica and NOTIFY them of it as they can often get some things through IF they have them on their manifest before they go there. Also add a note "Personal - Used . . . "
(more on this topic later as there are LOTS MORE points to add!!!)