I see in the recent activity page that "all times are in UTC; the current time is 2010-07-29 10:20:15Z"
Can I change this to reflect local time?
Nope, all times will stay in UTC and cannot be changed for the individual user. There have been requests to change this, but all have been declined thus far.
To one advantage, though, all site operations like the reputation cap and the Enthusiast badge series are also measured in UTC, so it's something consistent to monitor.