I have been on the MIJE hostel website, but still have a number of questions. Do the rooms have a bathroom and shower ensuite, or are they down the hall? Does the word Marais refer to a section or arrondisemont of Paris? Are all 3 hostels right near each other, and is one address nicer than the other? Is the surrounding neighborhood safe? I notice you can only book 45 days in advance, which makes me a little uncomfortable waiting until April 15 to book for June 1. Thanks for your input.
The Marais is a section of Paris in the 4th arrondisment. It's on the north bank of the Seine, very centrally located, directly north of Ile St. Louis. (about 2 min. walk) It's a safe area with lots of great cafes, restaurants, and shopping. Beautiful architecture. They are about a three minute walk between the three, but I am not sure if one is nicer. I would not worry about waiting to book until April 15, just send your reservation as soon as possible. You shouldn't have a problem finding room. If you have questions about the three hostels and what they offer, I'd e-mail the hostel directly. At least one person there will speak English.