What a fabulous time you will have in Spain! My husband and I were there this past June as well and it was one of THE best vacations we ever had. We started in Granada and were there a couple of days to enjoy the city and their jewel, the Alhambra and then took the train to Madrid for the rest of our time in Spain.
This is just my opinion, but 6 days in Madrid is a lot. I know you are counting on one extra day for a side trip to Toledo, but I would pack in as much as you can while you are there. Spain is one of the most beautiful places on earth and although Madrid is fabulous (I lived there for a couple of years many moons ago), I would recommend you add in additional side trips...you will find that you can still probably see everything you want in Madrid. I would encourage you to do a day trip to El Escorial (home of the Spanish Inquisition) and Valle de los Caidos (a memorial to the victims of the Spanish Civil War). The train ride is about 25 minutes and it is an experience you will never forget. I would also highly recommend a day trip to Segovia. The Alcazar is magnificent and so worth the trip (we spent the entire day exploring this gorgeous castle).
With regard to Madrid, we walked from one extreme to the other and loved it. We did the walking tour that Rick has carefully laid out in his book and it was fantastic. We covered absolutely everything he mentioned (Gran Via, Puerta del Sol, Plaza Mayor, etc. etc.). We walked to the Royal Palace and enjoyed about 4 hours exploring everything it had to offer. While we were looking through our book, a young lady asked us if we found it to be a helpful tool (a resounding "yes" from us!)...it turns out that she works for his company and was there to gather updates for the newest version of his Spain volume (talk about a small world!). After lunch, we walked to the Retiro Park and enjoyed the afternoon people watching and soaking up the sun (don't miss the Crystal Palace).
Another day, we took in both the Prado and Reina Sofia museums. We didn't encounter any lines, but that is because we purchased the Madrid card which let us avoid the lines altogether. I would just say that if you purchase it, remember that the clock starts ticking the moment you use it. You will want to plan out your activities so that you get the most out of it (you can buy it for a single day or more). After the museums, we then walked back over to the Retiro Park and had a lovely afternoon picnic there.
You MUST have chocolate y churros. Imagine hot chocolate with the consistency of a thick pudding and fried dough...to die for!!! You can get this anywhere, but I would especially recommend Chocolateria San Gines...they are a an institution! Churros are fantastic, but I prefer the Porras (they are the same, but a fatter and more delicious version of the churros (I bet you cannot tell how much I love them :-).
If you are still exploring where to stay, I cannot say enough wonderful things about Room Mate hotel. They have 3 locations in Madrid and are perfectly situated so that you are close to everything. We stayed at Room Mate Laura and it was phenomenal! The staff were so helpful and kind and the breakfast for 8 euros is a really good bargain.
With regard to weather, I would say pack a light sweater or jacket (I took a sweater and a denim jacket to alternate and it was all I needed). We are from Tucson, and used to the wonderful dry heat (I truly love our weather!). It was in the low to mid 70s and pretty chilly in the morning, but by noon I was able to take off my sweater and go sleeveless. Pack an umbrella just in case. It only rained once and even then it didn't last too long.
Just so you know, everyone speaks amazing English! I do speak Spanish (having lived there myself), but I noticed that they frequently responded to me in English. I obviously did not retain my Castillian accent :-).
I hope you have a phenomenal time!!!