We had a rental car as we went to Soberania National Park, but after dropping the car off the day before the flight we had to get back to the Marriott Courtyard. The walk to the bus isn't that far, but they don't take cash for the fare. We did find kindly locals who swiped their passes to get us on board and we offered double the cost-around $1. The buses are crowded and we had to stand until someone got off vacating some seats but we weren't going to pay $30 rip-off for a taxi!

The next morning, we did the same thing in reverse to catch our flight from PTY-LAS with carry-on backpacks. We never did find out where to buy bus passes but it was no trouble to offer the locals double bus fare in exchange for swiping their pass. If the bus had been late or too full we would have tried bargaining with a taxi for around $5 from Metromall/Courtyard to the airport and willing to hop off on the street outside the airport and walk in, in case the taxi had to pay a fee to enter the airport but buses were arriving promptly.