The coconut fiber does dry out very quickly in the heat of summer - I can't even use them here in zone
6 because I would need to water them several times a day.
I have grown portulaca in hanging baskets that have done very well and comes in nice bright colors. They can take heat well. Impatiens can handle early morning sun and then shade for the rest of the day, but will wilt if it gets too hot. Some people like to grow geraniums in hanging pots - they shouldn't be too expensive.
Do you need to use the coconut fiber in the pots, or can you use soil instead - are they solid pots?