I agree Monterey isn't all that, nice enough and beautiful location but pretty forgettable as a town. The whale watching was fantastic 4 years ago when last there though.
Yosemite is relatively quick to get to from SF, and if you want a much more pleasant casino experience, you can easily do Reno and then Lake Tahoe at that time of year. We drove across from Yosemite in April and the roads were just about good without chains, so September would be fine. Reno was a great little place, and so much fun. Really local feel to it, and the bars were just so welcoming. Can't wait to go back there at some point. Tahoe is stunning too.