The first time I visited family in Dubai I actually flew into AUH (due to a cheap deal with BA) and got a taxi to their home in Umm Suqeim (next to the Burj al Arab). Considering the distance involved, the taxi was incredibly cheap. So a taxi is always a useful alternative should public transport not work out.
Ladies & gentlemen this is Captain Tobias Wilcock welcoming you aboard Coconut Airways flight 372 to Bridgetown Barb
A taxi from AUH to anywhere in Dubai is a set fare of 225 AED. This is the quickest and handiest option.
The Etihad coach is free if you are an Etihad passenger. It will drop you off at The Dubai Marina Mall or Chelsea Tower, Sheikh Zayed Road in Dubai which are the locations of the 2 Etihad offices in Dubai. From there get a taxi or the Metro direct to Dubai Airport.