How can i go to my old elementary school and just pop and say hi ? ASAP?

There are a few things you can try. If the school has its own website, try visiting that and see if there are ways there to contact the staff. If you know the street address of the school, you can try writing a nice Christmas card to a few teachers, or to the special one you like best. You can ask them if there is any type of 'open house', visitor's day or other function that people can come to that would let you visit with them.