Salt will not harm IDY, that's another old tale that is perpetuated by writers who write rather then bake.
Modern yeast strains are more tolerant to salt than older strains but because salt is a hygroscopic substance and can leach fluids out of yeast cells by osmotic action and impair the yeast's performance, it is best not to let the salt remain in contact with yeast for long--as brief a time as possible. In Naples, to make sure this doesn't happen, the practice is to thoroughly dissolve the salt in water before adding the yeast or starter. That is what I would recommend, especially to beginners, in order to lessen the likelihood of harming the yeast. In my opinion, it is not worth losing a pizza or getting sub-par results just to avoid a simple prophylactic measure.
In addition to rehydrating ADY in warm water, it can also be added to the flour and used with water at a temperature of up to about 120 degrees F. The flour in that case buffers the ADY from the higher water temperatures.
None of the forms of yeast are fond of very cold water since that can shock the yeast and degrade its performance. However, in the case of IDY, when added to the flour, the buffering effect of the flour can offer protection to the IDY so that it can tolerate colder water. Usually, one would use colder water in order to achieve a low finished dough temperature for a prolonged cold fermentation that might run to several days, or if the dough is to be frozen. Under normal circumstances, one would use a water temperature that will achieve a finished dough temperature of about 75-80 degrees F for a home refrigerator application or about 80-85 degrees F for a commercial application using commercial coolers that run several degrees cooler than a home refrigerator.
There are also a couple of applications where IDY can be rehydrated. If one uses a mix/knead time that is less than about 4-5 minutes, or unless one is using a vertical cutter mixer, it is a good idea to rehydrate the IDY in water at a temperature of about 95 degrees F (see Reply 5 at
http://www.pizzamaking.com/forum/index.php/topic,14376.msg174903.html#msg174903).
I have used ADY dry (without rehydration) but that is advanced stuff where you have to know what you are doing and why, and how to adapt dough recipes to accommodate dry ADY. An example of this practice is given at Reply 48 at
http://www.pizzamaking.com/forum/index.php/topic,6758.msg64308/topicseen.html#msg64308.
Peter
