Hi madbiochemist!
I'm so glad I've found this thread! It seems very difficult to find other entering PhD students at JHU. I'm starting the PhD program in computer science there in fall. I visited a couple weeks ago so I got a chance to look around a little. Baltimore doesn't seem so bad -- definitely better than the reputation it has, and the JHU campus is gorgeous. Of course moving can be kind of tedious... But I'm excited!
Re: summer, I have a job here in the bay so I'm going to be showing up in August... But I would also be curious to know how many PhD students are planning on moving to Baltimore earlier. I had a chance to talk to a lot of the faculty and students there and I got a lot of recommendations for areas to live in, things to do, etc. -- also, I spent a weekend trucking around the city to check out the various neighborhoods. I'd be happy to share notes! As far as actually finding housing, it seems like the go-to resource will probably be craigslist (as usual). I was hoping JHU would have some ways to connect with other students as far as housing situations goes but so far I haven't found anything. Definitely let me know if you have any other ideas.
In the meantime, I've created this FB group for Fall 2015 incoming PhD students: https://www.facebook.com/groups/988481864517802/. Feel free to join -- I'm hoping it'll at least provide an opportunity for students to share ideas and get to know each other a little before the semester starts.