My wife Heather Blenkiron has been answering questions as the TripAdvisor "Destination Expert" for Galapagos for many years (she's answered nearly 3,500 questions so far).   

People often turn to the TripAdvisor Galapagos forum for advice, or for recommendations on this or that travel agency.   Heather's answer is invariably "no matter what agency you choose, just be sure they are Galapagos specialists, that they know what they are talking about".   

We are working out of our Victoria, British Columbia "office" these days (visiting family) and we were amused by the large bus shelter posters around town advertising a Galapagos trip, sponsored by a travel company that sells trips all over the world.   They send a lot of people to Galapagos every year.  But the picture on their poster is of an iguana not found in Galapagos.  Clearly, this company, one we like to call "the IKEA of travel agencies", cannot be considered a Galapagos expert.  

Below, the bus shelter advertisement showing a mundane, run-of-the-mill, dime-a-dozen green iguana, found from Mexico to Brazil (but NOT in Galapagos)

 

And now, below, the magnificent Galapagos Marine Iguana, found ONLY in Galapagos