I really like the Tropicana. Its extremely close (second one in from the crosswalk), has a nice pool area and a free breakfast. The room was super clean and the staff very friendly and helpful. It took us less than five minutes from our room to the turnstiles. It has some nice touches and again, the fabulous location, recent refurb to all their rooms and the free breakfast made it a real winner for our family. I have seen pretty much great reviews of the Tropicana here on Disboards lately. Of the four offsite motels I have had stayed at, this one was our personal favorite due to the location, staff, pricing and free breakfast (basic but free). I doubt I'll stay anywhere else again, this one just fit our bill the best.
I also do like the Howard Johnson's, its a bit further but still very walkable (closer than the Sheraton). It has some lovely grounds, less of a motel feel and two very nice pool areas. I do prefer the location of the Tropicana but love this property as well. Its also next door to Mimi's which is a wonderful restaurant. The Hojo doens't have a free breakfast but has a small store that sells things like milk and cereal for a very reasonable cost. The rooms are nice sized and some have greata views of
Disneyland. If you pick this one, make sure you specify that you want a non freeway side room, some of them are on the side that faces the I-5 and can be very noisy.
Good luck, staying offsite will not diminish the fun and magic of your trip at all, and as you say, if you won't use the amenities of the onsite properties, why pay for it! Good luck with your planning!