I think Curves is an excellent choice for someone who is just atarting to exercise, or returning after a long time off. The beauty of it is that you work at your own level, and you can skip any station that is too difficult for you with your various injuries. The people who work there are helpful and supportive, and so are the other members. Working on the machines regularly will help you build up your muscles, which will make walking easier and also help you with your blood sugar control.
If you are already fit, or have worked out at a regular gym or fitness center in the past, you may find Curves doesn't give you enough of a challenge. But they usually will give you a free week to try it out, so you have nothhing to lose. Their monthly charge is very reasonable too. I no longer belong there, because fortunately I have progressed to a higher level, but I know plenty of people who have belonged for years and it works well for them.