So as far as I know, there are two and a half lounges at SJO. There's the new Copa club (in partnership with United) that accepts a whole bunch of different people for access, but includes United Club members (and United Club one time passes), *G on Star Alliance flights, and some form of Priority Pass (didn't check to see if my Priority Pass Select would be accepted since I used my United Club credentials to enter). After you get through security, hang a left and walk towards gate 4; the club is on the left hand side downstairs. At least on Sundays, it opens sometime between 5am-5:30am and I have no idea when it closes. For the life of me, I couldn't find the operating hours on the web anywhere. There's light snacks and you can pay for drinks or more substantial food. There are no views outside. The restrooms are kinda small. There were a couple computers available, but I don't recall if there was a printer. The other one and a half lounges are also right near gate 4, but you head right and upstairs to the Avianca / American Express lounges. They share an entrance, but American Express of various forms (including Platinum card) will send you to the right through a glass door into a small room with free booze (Chilean wines, Johnny Walker Black, and some rum, vodka, beers, soft drinks, and bottled water), light snacks, free wifi, and a great view of the tarmac and runway. The Avianca lounge is larger, but I have no idea what they've got in there as I didn't have access. It's a *G lounge for folks departing on Star Alliance flights though, among other access criteria. If you're connecting from an international flight through SJO, you'll have to clear transit security before being able to access the lounges.