I get up around six .Is "around"an adverb or an preposition?

In this sentence it is an adverb, not a preposition, see below ADVERB: 6.

If it was a preposition it would be talking about how it relates to a place...We went travelling AROUND China.

From Webster's Dictionary: http://www.websters.com :

Around as an adverb:

1 a : in a circle or in circumference <the wheel goes around> <a tree five feet around> b : in, along, or through a circuit <the road goes around by the lake>
2 a : on all or various sides : in every or any direction <papers lying around> <nothing for miles around> b : in close from all sides so as to surround <people crowded around> c : in or near one's present place or situation <wait around awhile>
3 a : here and there : from one place to another <travels around on business> b : to a particular place <come around for dinner>
4 a :