MikeStuy -
When I said Q at Prospect Park I meant "over near Prospect Park" - the Parkside stop is about a 15 minute walk. And that area, over near the park, is pretty OK and close to school. When I say OK I mean that the necessities (grocery stores, produce markets, laundromats) are plentiful along Flatbush Ave, and while it isn't pretty, its safe and the rents, especially if you share, are good. I've lived over here for about 2 years, and never had problems, and being right near the park is great.
Commute-wise, its pretty close - when I was testing out the distance pre-interview, I walked there and back in one washing machine cycle, which puts the round trip at about 30 minutes. I can ride my bike there in about 5/7 minutes. The area is known as 'Lefferts Gardens'; common folk don't know the name, but you do see it used in real estate ads. If you want to try to stay along the 2/5 line, and the Slope is not coming through for you, also try out along Eastern Parkway as far as Franklin Ave (Brooklyn Museum/Botanic Garden area) where the subway lines split - an OK area and also a reasonable subway commute. And check out Prospect Heights, because that can put you near the 2/5, just on the other side of Flatbush from Park Slope. Might be a little cheaper, too.
I think a high percentage of 1st years live in the dorm, just because its hard to find a place, esp. if you aren't already in the area.