Of the programs you mentioned, we know people who’ve attended Interlochen, UNCSA, TPAP and Boston Conservatory. They are all excellent programs.
If you want to be in a city, the first 3 would not be the place for you although they all offer excellent training. They are not near a large city.
Boston is a large city in my book so not sure what you meant by “but I’d rather be in a larger city” next to Boston Conservatory. BoCo does offer excellent training.
I’m afraid many deadlines for the programs above may be past for this summer. But it may still be worth applying in case they still have openings.
Here are a couple of other programs you might consider that are true acting intensives:
http://www.playhousejuniors.com/meisner-teen-conservatory.html
http://www.pace.edu/summer-scholars/program-overview
You are doing the right thing in vetting these programs thoroughly. Summer programs can be a revenue generator for many schools, so make sure you are getting exactly what you need. Don’t be swayed by fancy marketing. Get first hand information on what these programs are really like.
The good news is, if you have not had much training at all, any of these programs, including the ones that are not near a city, will provide you with some good basic acting training. If you let us know what state you are in, perhaps we can suggest some programs that may be more cost effective for you.
Best of luck to you.