My daughter and I are visiting DC this summer. There is a direct flight into Dulles that looks tempting, but our hotel is in Alexandria. The hotel has a shuttle to/from DCA, but not Dulles. How much of a hassle is it to get from Dulles to Alexandria? It is about 24 miles, so I'm guessing a cab would be pretty expensive. Should we go for the longer itinerary (one stop) and fly into the closer airport, or manage the trip to and from the more distant airport. We are both adults, if that makes a difference.

My airport of choice in the DC area is BWI. The advantage of having a METRO stop at Reagan National would tempt me to fly there even if the fare is $50 higher just to avoid the bus/train/taxi hassle from Dulles.
The only time I flew to Dulles other than transfer I rented a car to visit northern Maryland.

We've just been dealing with the same problem. Our solution was to take the airport shuttle from Dulles to Reagan. They charge $44 for two people, sharing the van with other people. You reserve the shuttle online and we had to pay in advance. www.theairportshuttle.com. From there, your hotel shuttle can pick you up. Hope this helps.

If the cost of flying is the same, I'd fly into Reagan.

A cab would be in the range of $60 each way from Dulles to Alexandria, possibly more in the height of rush traffic.

If you do fly into Dulles: You can take the Washington Flyer bus (runs every 30 min) from Dulles to the West Falls Church Metro. ($10 one way/$18 round trip) Ride the Orange Line Metro to Rosslyn, change to Blue Line train to Alexandria. Get off at Reagan National and find your hotel shuttle. If your hotel is in Old Town in the vicinity of King Street, you can ride the metro until you get to the King Street station and walk or take the free shuttle that runs up and down King.

It's not difficult but it is more of a hassle then flying into Reagan.

http://www.washfly.com/flyer_bus_schedule.htm

A cab is going to be about $60-70 depending on where in Alexandria.

Reagan is one of very few airports I choose over it's regional counterparts (Dulles and BWI) even though I have to change planes to get there. I just prefer the convenience of taking the metro once I'm there.

If it were me, I'd probably book the non-stop flight to Dulles. I always choose a non-stop flight whenever I can, even if it means driving to Dulles or BWI Airport (and I live 10 minutes away from DCA).

First, there's always less chance of something going wrong (mechanical or weather-wise) if you only have to deal with one flight and one airplane.

Second, flights in/out of DCA are generally the most expensive of all the 3 area airports, so I'm guessing your flight to Dulles is going to be cheaper than the flight to DCA. While the taxi fare is a bit steep (and $60 - $70 is a good estimate of what you'll have to pay to get to Alexandria), it still may be cheaper to fly to Dulles and pay for a taxi than fly into DCA. Getting a taxi at Dulles has never been a hassle for me.

Another option is taking the 5A bus from Dulles directly to the Rosslyn Metro station where you can then pick up the Blue Line Metro to the King Street Metro station in Alexandria. The fare is $6.00 and here's the link to the 5A schedule:
http://www.wmata.com/bus/timetables/dc/05a.pdf?n