We were in Colon for Thanksgiving on the Carnival Freedom. I took a chance and contacted Ricardo Laurie (based on older feedback in this forum).
He turned out to be great for the family and myself. Much cheaper than Carnival tours ($180 for the day 6 hours, family of five.) We went to the Panama Canal and then to Portobello. You can customize any tour you wish. Perfect English, and went out of his way to be helpful. Just a normal taxi cab, but well worth the price and personal itinerary.