It's not easy getting there from the 'Peg.
GO JETS GO !!! Had season tickets for many years when they were in the WHA. Hope they bring back some of the guys for the first game.
The daily non-stops into Liberia are from Dallas, Houston, Atlanta and Miami. Never heard of one from Phoenix.
Is the Condovac Saturday-Saturday?
You can get a Friday-Friday charter out of St. Louis for cheap via USA3000. They don't have their winter schedule posted yet, though.
Air Canada vacations has a Sunday-Sunday charter out of Toronto. There are also Monday and Thursday charters out of Toronto.
Air Canada and TACA have scheduled non-stops out of Toronto into San Jose.
The absolutely cheapest way to get to Costa Rica is with Spirit Air out of Fort Lauderdale. Just over $300 return. If you can get to Fort Lauderdale or Miami for cheap, this might be an option. You can also leave from Chicago or Dallas. They show Toronto on their route map, but don't be deceived. It's actually Niagara Falls, NY. They fly into San Jose.
If I were you, the best combination of cheap flights without long layovers is to fly out of Minneapolis. Less than $800 with only a 1 hour layover in Charlotte with USAir. Just drive or bus down the day before.
You didn't say where you were spending the 3rd week, and whether it was before or after Condovac. Maybe flying into SJO and out of LIR makes more sense, or vice-versa.