Yes, you can have a happy hydrangea in your sunny spot but instead of the blue balls of the big leaf hydrangea macrophylla go with the more heat tolerant hydrangea paniculata or Pee Gee hydrangea. The compact cream and pink flowering hydrangea called 'Strawberry Vanilla' hydrangea paniculata or the all white dwarf "Bo Bo" hydrangea can take sun and will not grow huge up against the house. I would not worry too much about black spots on the hydrangeas you see for sale now. That is most likely a leaf blight from overhead watering and nurseries in late summer must water differently than you will once you get your plant in the ground. Hydrangeas lose their leaves in the winter so next spring you will have a fresh start with clean foliage. Now if you have your heart set on a blue blooming hydrangea you will need a spot with shade in the afternoon or else the blue bloomer will wilt in the heat. You can easily keep a blue hydrangea from turning pink by making sure the soil is acid. Just add aluminum sulfate around the roots in early spring and this will lower the ph of the soil for blue blooms - but this only works on the big leaf or pom pom round blooms of the big leaf hydrangeas. White hydrangeas stay white and pee gee hydrangeas (the sun tolerant ones)  do not change color. Remember that hydrangeas do well in large containers so placing a pot where it gets morning sun and keeping the plant well watered in summer is another way to enjoy blue blooms.  Keep growing, Marianne Binetti