Ruby,
OK, see if youcan get someone in San Pedro to go to the agriculture office (next to the customs office) in San Pedro (white corner bldg, just down from the Travel agency), and fill out the paperwork there for you. It cost $10 BZ per animal. They will fax paperwork over to the airport for your arrival. That's the easiest way. If my husband was there now, I'd get him to do it, but he is still in the States.
Have you checked with the airlines yet about allowing 3 animals on the same flight? I've been told the max is 2 (for in-cabin-- and I'd think with yorkie's, you'd want them up front).
Good luck!!
Cheerz,
Vicki