There are four audio clips of Sergio at Media Day over at the Oregonian, http://blog.oregonlive.com/blazers/2007/10/listen_up_2.html.
On thing that is clear right off the bat is that his english has improved--a remarkable improvement in understanding it and a decent but not spectacular improvement in speaking. At some point the interviewers even compliment him on his improved english skills.
The other info from the interviews that i found interesting is he doesn't seem at all deterred by the things Nate has said, and says his plan is to go in and play hard and earn a spot.
Also, when asked what parts of his game he wanted to work on, he said he wanted to improve all aspects,and when pressed for details he said, in this order: 1) defense, 2) shooting, 3) less turnovers. from his lips to god's ears, i say! he definitely gave the right answer, let's hope he really does improve all that stuff.