Have you checked out King Farm (walking distance to Shady Grove metro and has a dog park)? The apartments are either part of A)The Huntington at King Farm or B)The Residences at King Farm. The major differences between the two are school districts (those in A are MUCH better) and amenities (B were built to become condos so therefore have nicer cabinets, etc. but the development forclosed I guess because now they are being rented out for less than the apartments built to be apartments in A).
A =
Huntington at King Farm Apartments Rockville, MD - Apartments for Rent in Rockville Maryland
B =
Residences At King Farm
Have friends that live in A and B and both like it so far.
Fallsgrove also has nice apartments but I don't know as much about them.
Good luck in your search!