I would personally leave the mash temp at 150F. The lower temp will give you a drier beer in the end, which I prefer. Generally speaking, lower mash temps (148-150 ish) and longer rest times (90 min.) will yield a drier, more fermentable beer. Higher mash temps (153-154) with a 60 min. rest will cause your beer to have more body and fewer fermentable sugars. So it's really personal preference. I'd say stick with the recipe until you feel comfortable manipulating the mash temps and creating your own recipes.
Either way I think this looks like a good tasting IPA. If I were making it and I wanted to find a way to give it a little extra hop flavor, I'd dry-hop with another 1 oz. of cascade during the last week of your fermentation...
Have a great brew day!