Just a thought. I would love it if crochet magazines would put the actual weight of the yarns for the patterns because some of the yarns are not easily purchased around here. I would love to be able to purchase something comparable in weight.
I can't speak for other magazines, but for each pattern in Interweave Crochet you will find in the "Getting Started" section at the beginning a yarn ball icon. This yarn ball will have a number in it that corresponds with a yarn weight, i.e. 1 is lace weight, 2 sport, and 3 DK. There is some variability even within the individual weights, so if you are substituting yarn it is still important to create a good swatch. You can also frequently find weight information on the yarn company's website if the particular magazine you are working from does not include that information.