If you want to add vines for privacy, I would definitely recommend not allowing them to grow on or directly contact the wrought iron with that type of reflective heat as the leaves have a good chance of frying. I have an all-aluminum fence with a half sun (morning sun, NE-facing) balcony and when it hits the 90s, those leaves directly contacting and getting sun reflection from the rail eventually fry - or may become damaged after extended exposure like that. Often the signs of damage are delayed until it gets cooler but crispy leaves do eventually appear.

You could try a lattice or other structure in front of the rail and train the vines on that, which would help keep them from contact with the metal. And as a note, unless the weight is an issue, you shouldn't have to shy away from larger plants. I recall reading a few articles in the past that tried to explode the myth that one must have "small plants" in "small spaces". A few well-placed larger plants can be just as effective, according to the articles. If you did want to go with vines (and although it might be a little late to start it this year), you could consider moonflowers, which love the sun, and with a large enough pot, would completely engulf the rail. Similarly, morning glories or clematis could be trained to do the same (where the clematis would be perennial).

Wow, bluephy! 102! There are certain containers you can use for your plants that can handle the heat better and allow you to water them more heavily without worry of drowning them. Putting up a lattice fence for your vines to climb will work but may take some time. I would suggest planting some strawberries for a bit of colour as they do well in the heat. I've fallen in love with my apartment's balcony garden and love being able to relax with friends munching on fresh wild strawberries.