H1B去加拿大和墨西哥要签证吗?
-Need Canada visa to enter Canada; not need Mexico visa to enter Mexico if you will return to US within 60 days.
回来时要重新申请H1B吗?
-Not need H-1 visa to return to US if you will come back within 30 days, otherwise need to get the H-1 visa to come back.