Days Inn - Lake Buena Vista near Downtown Disney is less than a mile away. I'm not sure about walking, but you can get it for $36 a night!
Hotel Royal Plaza is actually in DTD - or within walking distance. Its $72 a night with every 4th night is free. You also get a FREE Upgrade to a Deluxe Tower Room. Room Discription:
Deluxe_Tower_room_with_2_double_beds (or 1 King Bed) This room features an oversized bathroom with a Roman tub, and
Bath and Body Works amenities. Relax in the large sitting area with a sleeper sofa. From this room, you will enjoy superior views of the resort and it's surrounding areas, with some including Downtown Disney views. Complete with Tropical decor and light wood furnishings, this room also includes a color television, Nintendo, in-room safe, ceiling fan, mini-bar, hairdryer, iron/ironing board, dataports, coffee/tea maker, voicemail, interior corridor and a private balcony.
When I did a sample trip for my trip for Aug 6-14 (9 nights) it only totaled $561.96. You can't beat that with a stick!!!!
Here is the website:
http://dir.travelzoo.com/lodging.asp?intCategory=28&id=151259