You should also think about which aircraft you would like to fly. Just thinking about the most popular aircraft but your top choices are either R22 or Cabri G2. Once you know that, then look for the school with the most experience in dealing with that helicopter and what they can offer you other than best price.
I agree with Hughes500, pick somewhere with changeable weather, will make you a better pilot with good judgement of your surroundings.
Best of luck