Hola! I have a school smack in the middle of kite beach.
www.kiteboardingcabarete.com. There are a few things to consider when choosing a school.
Location: There are a few places on Cabarete Beach that are in the "wind shadow" so you will end up walking down the beach to get to the wind zone. In my (maybe biased) opinion, learning is easier on Kite Beach because there is usually not a shore break. Kite Beach is also much less choppy because the reef is closer which protects our little bay. I learned in Cabarete Bay myself and as soon as I discovered Kite Beach I never went back! That being said, in the summer the beach on Kite Beach can get smaller making it a littler trickier.
Equipment: There is expensive equipment and there is cheap equipment. That price has to be worked into the price of the lessons. You can do quick easy research to look into that factor to see if the price coincides with quality of gear.
Hours: I don't care what anyone says, most people need about nine hours of lessons. Some schools sell you six hours, but you will more than likely need the other three hours to get up and riding. Six hours is cheaper than nine hours on paper, but it will end up costing you more usually in the long run.
Certifications: Some schools have IKO some don't. They have to pay for that if they do. I have seen good IKO instructors and IKO instructors that look like they just learned to kite. Same goes for non IKO. To me, IKO isn't the only thing that makes a good instructor.
In general, anywhere with a brick and mortar school is running a pretty legit kite business here, but you still get what you pay for as with anything. So, I think if you consider the above you will be able to make a sound decision.