Just got back from a fantastic trip to China, did a lot for research on this site, hope this helps anyone who is also planning a visit.
You can use the public transport to get to this site. I caught the 611 bus 30m west of the Melody hotel to the railway station. You need to get to the east car park, try and locate the big white China Post Office Building.
You need to catch the Tourist Bus Route #5. You will be approached by scammers trying to get on their mini busses, ignore them and head for bus #5. The bus cost Y7 and took 1 hour to get the TC car park. Follow the other Chinese tourist to the ticket office which is a 5 minute walk. Buy your entrance ticket and there is another counter for the electric car ride to the TC complex. You will be pestered by guides, but I didn’t take one. I visited the exhibition hall first. The exhibits were very good but there are too many people taking photos like no tomorrow and spoilt the ambience. Pits 1, 2 and 3 were amazing.
Upon exit follow the signs to way out. There are lots of shops on the way, I ended up on the roadside somehow and caught the bus back to Xian from this point, however I was trying to get back to the car park where the bus had dropped me off on the way in.