Join Date: Oct 2007
Location: Catania, Sicily(CTA)/South Jersey (PHL)/Houston(IAH)/Red Stick, La.(BTR)/airborne in-between
Programs: United Plat (1MM), AA Plat Pro, ITA/AZ Freccia, Hilton Diam, Bonvoy Gold, Hertz Prez, IHG gold
Posts: 3,831
For out-bound to Costa Rica from Canada IAH would be a very good choice,a s others noted, you go through US CBP in Canada (normally).
Flying back to Canada IAH is one of the few airports with the fast track immigration lines. If you are not checking a bag there are dedicated lines and if you are checking a bag int'l to int'l on United you do NOT have to claim your bags and do Customs checks in Houston, just immigration.
Yes you would have to do the TSA Richard Waltz but that is dedicated also (not like at EWR where one goes back into the main terminal).
Good luck.