In the north, hydrangea macrophylla is deciduous shedding all its leaves in the winter. So no, removing all the fungal infected leaves and disposing of them will not kill the plant unless it becomes a chronic problem.

Have a look at Clerodendrum quadriloculare if the hydrangea doesn't work out for you in S. Florida. That might be a good substitute for what you miss.

You should be able to cut off the infected foliage by cutting the petiole string that connects each leaf to the stem. Alternatively, let the foliage drop on its own; then pick up the leaves and throw them away in the trash.

Avoid overhead watering to minimize fungal leaf spots. Use drip irrigation or soaker hoses instead of sprinklers.