In the end I DID parade with Salgueiro on the Sunday of carnival. The costume was indeed hot, and heavy, but it was all manageable. The trick is to drink pots and pots of water beforehand, and not to put on the thickly padded cloak, or the hat and shoes, until the last possible minute.
There was a certain amount of unease at having a foreign gringa in the ala, but in truth I was far more experienced at parading in the sambodromo than many of the others in the Ala, who were largely Brazilian tourists and rich first timers from Zona Sul. And parading in an ala is much shorter than parading in a Bateria. And parading so many times in baterias gives one excellent training in how to behave in a Grupo Especial samba school parade.
Theres 3 important jobs an ala member has to do. The first is to sing the song, which is achievable even by foreign gringos if they are persistant. The second is to be animated and to keep dancing, or at least moving around, throughout the parade, without losing your place in the line. The third is to look ecstatically happy throughout.
Jobs 2 and 3 are hard to do if the costume is too hot and heavy and the shoes too uncomfortable. Even the Salgueiro veterans in the ala were having problems looking as if they were enjoying it by the end. By a third of the way down the sambodromo the burning pain from the simple flat shoes extended from my feet up past the knees. Still, had to keep moving, smiling, singing and dancing.
But as a veteran of the sambodromo I was prepared. I drank enough water before the parade to avoid dehydration, despite the liters of sweat produced by 40 minutes of dancing in that sweltering costume in nearly 40 degrees of heat. There were paracetamol and light clothes in a bag hidden inside the voluminous padded trousers. And a pair of super comfortable sandals strapped to my back, completely hidden under the huge padded swirly cloak. Immediatly after the parade, whilst others stood there, sweating, it was off with the costume, on with the clothes and sandals and down with 2 paracetamol.