Here's a link to spredsheets for all of the Hiland Lakes including Lake Travis. Lake Travis is now just about average for June / July but up about 30 feet from May.
http://www.lcra.org/water/river-and-weather/pages/historical-lake-levels.aspx
As for sailing safely, sailing Lake travis is different but can be done safely. The lake is actually a reservoir, and there are canyons leading into the lake that can cause sudden and dramatic wind speed and direction changes. Travis is a variable level lake, and there also can be sudden depth changes because of the underwater terrain and the not so sudden changes in water level variation. We have our sounder set at 20 feet that provides sufficient warning except for cliff-like underwater terrain.
Another difference is that the lake is long and narrow, and mean time between tacks can be in less than ten minutes.