We didn't take a bus; we had a car and drove. We spent a few days in Phoenix, a few days in Disneyland, a few days in Los Angeles, and a few days in Las Vegas. Of course, our trip was two weeks long. If you fly in to LAX or SNA and fly out of LAS, I think a few days in Disneyland and a few days in Las Vegas is very feasible.
We always drive from Vegas to DLR. It's worth it to us! I've only heard good things about the Lux Bus so if you don't want to drive it yourself and rent a car, it's probably worth the convenience of letting someone else drive and just relaxing.