Several Pentagon City hotels seemt to suit my needs well (two bedrooms, kitchen), but I'm concerned about the location as I'll be traveling for pleasure and want to see the main tourist sites. How far is it by Metro into the center of DC (Mall, White House, etc.)? More than 15 minutes? Would it be fairly easy to go back and forth, such as for lunch or freshening up or would that be too cumbersome? Many thanks for any replies.

Nothing is too far by Metro. Remember that DC is only about 12 square miles total, and that Pentagon City is just outside that line.
The metro system is the easiest I've ever used in any city - very comprehensive and simple to figure out.
I'd say it would take about 15 minutes for the trip - you are right about that.
Also, the exit for the metro lets you off right inside the Pentagon City shopping mall, so if you forget anything at hoe - well, it's right there at your fingertips!
Also, you will already be on the blue line, which is the line where all the major attractions lie.
When are you going? I'm jealous. I went to school there and I miss it!

If you're withing WALKING distance then you're in a decent location. And like TravlGirl wrote, nothing is far by Metro.

Try this website for times, costs, routing, etc from one point to another using combinations of walk, bus & metrorail:
http://rideguide.wmata.com

I catch the subway at Pentagon City every morning, and I can be near G-town in 15 minutes. It's really only one or two stops into Virginia, so you could also go back in the middle of the day and go back into the city.

There are good eating options in Pentagon City, every safe, and lots of shopping if you want to kill time.

You're much better off getting a suite with kitchen in DC proper, IMO. There are several 2RR w/ kitchen suites in DC. Since you always pay more for a better location, it will likely cost a bit more than places in Pentagon City.

Look at these 2BR suites w/ kitchen - the forst 4 are a walk to the sights and close to Metro. The last one is in a nice area but requires you to take the circulator to reach the sights:

1) Residence Inn Marriott Washington Dupont Circle

2) Doubletree Guest Suites Washington
Foggy Bottom

3) Homewood Suites Washington
Downtown

4) Korman Communities DC
Downtown

5) Georgetown Suites
Georgetown (the DC circulator can whisk you right to the sights)

http://www.dccirculator.com/home_page/

There is also Capitol Suites in Capitol Hill, SE, which is a great, a little bit quiet, neighborhood.

I agree that Capitol Hill Suites is a great location but I believe they are all 1BR + LR & kit. It is better suited for a couple (in BR) with the children on the fold-out sofa in the LR.

Staying in PC vs. DC? Unless you have a compelling reason to be there (like shopping or a large cost break), it's hard to understand why. Bardo offers some nice suggestions. On my list of possible lodging options, it's way down the list because of its almost complete lack of charm.

I appreciate the replies. I will definitely look into all of Bardo's suggestions, although I had looked at Doubletree and thought they only offered 1 bedroom suites with the sofabed. I'm hoping to treat my parents to a nice vacation (Mom's always wanted to see DC) but I want two full bedrooms and two bathroom w/kitchen so we can enjoy a relaxing breakfast with the Post. It kind of narrows the choices somewhat. My first choice seemed to be the Residence Inn at Pentagon City; I must have overlooked the one in Dupont Circle. For TravlGrl, I'm depating between early Sept or early Oct (got to get a freebie bank holiday in there). Cheers!