Hydrangeas do quite well in pots, so long as the pots are of suitable size. They will require more frequent watering than if they were in the ground, but otherwise, hydrangeas can be kept in pots for years. My guess is you'll find that dappled shade or morning sun will give you the best results in your zone, but you are likely to see some drooping during the heat of the day regardless of where you put them. You are definitely on the hotter end of their preferred range, but I don't see any reason why you shouldn't be able to get beautiful results. Good luck!

Actually, hydrangeas grow well in coastal SoCal - the Laguna Beach/San Diego area - which is a zone 10 (they also grow beautifully in Tampa, also a zone 10). Shade in the afternoon is a must and provide plenty of water during the hot summer months.