How do you know if a crossmember is going bad?

If you took it into a front end alignment shop they can inspect it. Usually the bushing get worn out.

Is it rusty? Bent? You can pick up used ones. http://www.allusedparts.com/ford/escape/2006/suspension_cross_membersubframe/

I think it's rusty. The mechanic told me that it needed replaced. All I can remember is that he said it was rusty.

Best to get it replaced then.