I'm in Panama City right now as well (till Wednesday), and I also had no idea it was Carnaval! That actually kinda sucks, since I legitimately have work to do and can't stay out all night partying. Yes, it's hot and humid, but as a native Texan I'm not fazed in the least.
A few trip notes:
1) My itinerary worked remarkably well, for those wanting minimal layovers. I was on the 10:30pm flight out of LAX (28), which was of course an A321T; had a 55-minute layover at JFK before AA 200 left at 8:05am; then had nearly an hour at MIA before catching AA 1532, which got me in at 3:30pm.
2) Note that AA 200 is on the
refurbished 772, not the old one that still has angled-flat seats (egads!). I didn't really
need a flat-bed seat for a three-hour flight
but its J product is now nearly as good as that on the 773. While yes, half of its seats face the rear, it's nonetheless significantly better than other planes with similar layouts, e.g. BA. All offer quiet and privacy. (Somewhat oddly, the
worst flight of the bunch was the one international leg, on a 738 with standard domestic F seating. They didn't even offer pre-flight cocktails!)
3) My original plan was to rent a car, since they're listed on OTAs as "only" $7/day (economy) to $20/day (for an SUV).
DO NOT DO THIS!! Upon arrival I noticed a customer in a heated argument at the Avis counter, which should have prepared me for what I'd find at Hertz. My "inexpensive" rental QUADRUPLED in price to $240 (!!) once insurance was added on ... and I was told this is "mandatory" under government regulations. (I do not know one way or the other if this is true, however.)
4) I took an Uber car to my hotel - and btw it's a flat rate of $25 plus tolls for all UberX trips from the airport to the city center. I've heard conflicting stories about taxis, but for the most part they should be avoided (unless Uber is in surge mode, I suppose).
Anyway, so far, so good. :-) Btw I'm staying at the Bristol, which I
highly recommend if you're wanting something more low-key than the Hard Rock or Trump. I also managed to get a fantastic deal on it (via OTA): $95 my first night and $110 each for the subsequent two.