回复：请问老师们，收到WELCOME LETTER，说绿卡PROVE 了，LETTER还说三星期内会收到卡。请问

我现在就可以工作了，还是要等卡拿到才可以。

-Technically you can work, but the employers normally will not allow you to work unless you show them the green card or EAD.

还是我可以用工卡工作？

-Yes before you get the GC or GC stamp.

还是我应该在护照上盖章才可工作？

-Yes, it is better.

另外WELCOME LETTER 说三星期内寄卡，是就三星期，还是可能会迟些。

-may be sooner or later.