When can I start going out with my newborn without incurring any real danger to her?

Caution for 2mo. Babies are gifted with much of mom's immunity @ birth which provides some protection. They are also exposed to germs @ birth that may wait to cause problems for weeks, some of which cause serious illness. If baby develops a fever in the first 6-8 wks, they are often hospitalized for tests & rx. Keeping them away from sick people can help u avoid a hospital stay. Going out is fine in healthy settings.
Now is OK. The potential problems with taking your young infant out during the first few months are not related so much to being outdoors as to the contact with others who might harbor a contagious infection. It is usually safe to take your newborn outside as long as he or she is appropriately dressed for the weather and extremes of temperature are avoided. Avoid crowds and sick people.