Hi Jim,
My wife and are were in the same boat a few months ago. We had our stamped paperwork but no cedula yet. We were required to purchase a forward on ticket when we checked in with Spirit in Dallas. The requirement seems to be more enforced on the US end than with CR – we have never been asked to see a return ticket from any agent in CR. On a separate occasion to the States with Southwest we were not asked about a forward on ticket. The adage “your mileage may vary” is very appropriate.
We now always just but a return ticket and front the extra money to buy a refundable one. Once we get in the country we have it refunded.
Best of luck,
Greg Seymour
IL Central Valley Correspondent