MS or MBA?

I have done my Bachelors in Telcommunication Engineering from Pakistan. I am planning for abroad studies in USA. I am interested to go for management career. I have following questions regarding before makling decision:

1. Should I do MS and then do MBA in MIS after some job experience?
2. Will my MBA have a value if I do it now instead of MS?
3. Can I do MBA after doing job experience in BS without doing MS?

Thanx for ur help.