I've stayed at the comfort inn on palm pkwy (just north of DTD). The rooms were clean and nice and the rate was decent.
the motel 6 on 192 across from old town is a really old hotel, and the bathrooms show it. But the rooms weren't terrible and the property was clean. Plus they allow for pets.
There's a Holiday Inn express on 535, just south of the Epcot entrance. I saw it when it was a La Quinta when it was first built, but it still looks the same. And it's only a few years old. The rooms where very nice and large, and there was a nice breakfast buffet. But I have no idea what the going rate is.
your best bet is to search hotwire or something to see what the going rate is. You can also check in the travel saver book, you can find them at McD's. And often times will have good discounts in them. Just remember, you can't reserve the room if you use it. it's first come, first serve. But when we used to travel to Disney on a whim for the weekend, we used these books a lot and found some great rates.