Unfortunately, that's one of the worst times of year for Yosemite because many of the waterfalls are mostly dried up in late summer and autumn until the rains start. Late spring and early summer are best there. Oh, well. It's still a wonderful place even without much water in many of the falls.
If you find it difficult to get reservations in Yosemite Valley, the closest of the towns outside the park is El Portal (which is still something like 30-45 minutes from the valley). It has a very good (and huge) motel, Yosemite View Lodge; it's not cheap, but the rooms are much nicer than in most motels, it has a reasonably good restaurant, and some of the rooms are along the river, which is nice. Motels in the farther towns of Oakhurst and Mariposa are cheaper and simpler.
Keep in mind that the roads through Yosemite park aren't fast. If you venture into the high country on the Tioga Road or the Glacier Point road (highly recommended, especially the latter - don't miss Glacier Point, whatever you do), you will be spending time stuck behind slow-moving motor homes on twisty two-lane roads. Allow plenty of time for driving.
Lisa
