I am sorry for this delayed reply to your gardening question. We are transitioning to a new Q&A system and your question was unfortunately lost in the transition. I have discovered it now and hope this reply is not too late to be of help.
There are so many plants to consider for your area I'm not sure where to begin. Some really tough choices for summer blooms are: Lantana (New Gold is a good one but there are many others with multicolored blooms), Tecoma stans 'Gold Star'(yellow bells or esperanza)(may not be perennial in your area), Salvia 'Indigo Spires', Plumbago (sky blue flowers), perennial hibiscus ('Flare', 'Red River', 'Lord Baltimore', 'Lady Baltimore', purslane/portulaca (annual flower), Salvia greggii, Salvia leucantha (late summer to fall blooming), Coreopsis lanceolata, Shasta daisy, and for winter you need to consider pansies and viola which are annuals. Shrub roses like 'Old Blush' and 'Knock Out' would be other great disease resistant choices for spring and fall bloom.
For more ideas here are some web references:
Regarding the hydrangeas I don't know if they will suit your setting since summer care is important. Most all bloom early and don't repeat well, although 'Endless Summer' may be an option if you are determined to try one.
Thanks for the question. Please stop in again soon!
Q&A Library Searching Tips