lodging reasonably close to the airport

Do you have an early flight? If not, I'd stay city center where you'd likely have more fun and take the reliable public transportation to the airport.

Not sure price for your date but I stayed at the Hilton Madrid Airport and loved it. Not small or B&B. I was there last October and paid just under $200 I think.
Room was modern, new, and the breakfast was out of this world!
I took the free shuttle both ways (I had a night layover in Madrid and early flight).

We've stayed at the Marriott Auditorium twice, most recently 2 weeks ago. Rooms are less than 200 euros per night and the free shuttle to the airport starts running at 4 a.m. It's clean, rooms are pretty large but basic. I recommend enjoying the day and dinner in Madrid before going to the hotel for the night.

Hi Susan, A few years back my husband and I stayed one night at Hotel Clement Barajas. Reasonably priced, modern, near restaurants and they had ( at least at that time) a shuttle service to the airport which we took for our very early morning flight to London. As has been suggested, if your flight out is not too early, you could consider staying in Madrid itself as there are lots of transportation options out to the airport. Give yourself plenty of airport time as Barajas is huge.

Not sure if it would influence your decision, but flat rate taxi to the airport is 33 euro, 24/7, less than 30 minutes from Madrid center. Metro is an option, but first trains do not start running until 6 AM.

Personally I prefer my last night somewhere with a nice stroll, a good meal, some people around.

This is, in my opinion, the classic mistake a lot of visitors make in Barcelona. And honestly, the same argument applies to Madrid too: it’s just not worth it.

Both cities have their airports pretty close to town, and there are several cheap and efficient ways to get around, from metro and train to bus or taxi. So, unless you have a very specific reason to stay near the airport, there’s really no need to do it.

Of course, not every part of the city makes sense for every trip. If the airport is on the west side of town, for example, it’s worth looking for a hotel in the western neighbourhoods so you don’t have to cross the whole city just to get to your flight, especially if you’re leaving at rush hour.

But in general, staying in the city is far more rewarding in every sense. You get the atmosphere, the food, the streets, the nightlife, the whole experience. That’s what you’re really there for, not some anonymous hotel by the runway.

And as a general rule, hotels closest to the airport tend to be in places that either have nothing interesting around them at all, sometimes even industrial estates, or in areas that are a bit rougher than average. In Barcelona, for example, some of the zones near the airport are definitely not the nicest or most appealing places to stay.

Very sensible, and informative post from Enric.

Your tastes may be different but unless I were arriving in either of those cities well after dinner hours, I would never choose to spend my last night near the airport. If you are flying back to the US, your flights will not probably not leave in the morning, so why waste an evening and morning stuck out at the airport?

I believe he was referring to Madrid.
When we have a mid morning flight we stay in town but for the west coast of North America flights are usually at 6 am. We then stay at Tryp Madrid Alameda Aeropuerto Hotel as they have a 24 hour shuttle.

If you are flying back to the US, your flights will not probably not leave in the morning, so why waste an evening and morning stuck out at the airport?

This is not correct. I flew from Madrid to the US in October and in the morning. I arrived at 7am at the airport for 9am flight and the check-in line for Delta was ginormous. I didn't have to check a bag so went straight to checkpoint/security. And I am pretty sure there were other earlier flights directly to US from Madrid.
I landed in Madrid at 8:30pm the night before so it was just a night layover for me. Staying next to the airport worked really well. I had a relaxing and delicious dinner at the Hilton Madrid Airport and a fantastic early breakfast next day.
If I had a full day to explore, I would have probably stayed in town and taken an early taxi to the airport.

I was referring to flights from Madrid to the US, but I mistakenly spoke only of flying to the east coast, when flights generally leave in the afternoon....so I always stay in the city, both Madrid and Barcelona, rather than out by the airports of those cities..

I know nothing, though, of flights to and from the West coast of the US and should have been more clear..