As bpaff has shared, the difference in current between US and Europe can blow out all of the circuits!
My own experience in traveling with blow dryers (as a student as well), was that even with the converter, the dryer was slower and it will take longer to dry hair so it just doesn't work as well. That's the reason why most hotels provide dryers in the bathrooms so you really might not need to bring your own. As for the curling iron, I'd recommend you buy one here if you can't do without!
Seeing Melany's post, she's confirmed that all you need for the Mac and iphone is the PLUG ADAPTER, no need for current converter. I also recommend you buy the plugs adapters at Walmart or Target (cheaper than here) in the travel section - I've got the box that has all the different ones incorporated and a switch pushes out the one you need.
Mid-April generally has nice weather already, but they can still be a bit chilly and you can expect rain on some days too. I'd suggest bringing light sweaters and a light waterproof jacket so that you can layer and take off/put on as needed. If you have a really small umbrella, bring it otherwise if the need arises, you can just buy one here from the many immigrants that sell them on the street for 5 euro and leave behind when you leave.