I am not sure if the airport tax is already included in the airfare. If not, how much is it? Or where can I find this out?
I am planning on traveling down to Ecuador during this Christmas. My route is USA-ECU-BRA-ECU-USA.
According to Wikitravel it's separate to airfare, like many South American airports.
It doesn't have the latest value, but does state that:
International departure airport tax was just recently increased in Guayaquil and is exactly $29.75 (January 2010). About 15$ cheaper than Quito airport.
It changes all the time on a government whim. Check before you leave. It is "almost" always included in the ticket but be careful, if it changes between buying the ticket and your flight date they will charge you the extra at the airport. I once had to pay an additional $15 and then loaned $15 each to a couple of backpackers who had "spent out" before getting to the airport. No dollar answer should be given, for example it is over $30 now.