If you take one of the taxis at STI it will cost you about $100 USD but if you call a taxi company not affiliated with STI it will be about $50 to $60 USD.
For 6 people I think you could count on something around $100US each way. I, personally, don't think you will find anything in the $50US - $60US range unless you speak Spanish and arrange for a non-tourist taxi to pick you up; if they can pick up at STI at all.
For around $100US - $110US (my estimate) you can get an English speaking driver who will meet your flight; contact Martin Espinal at espinal30@msn.com
If you take one of the taxis at STI it will cost you about $100 USD but if you call a taxi company not affiliated with STI it will be about $50 to $60 USD.
I cannot comment on STI airport but I have used a taxi service several times from POP airport where the driver removes his signs from the top of the car and just appears as a friend picking me up. His prices cant be matched so far.