I'm going on vacation June 30 to July 6. Should I risk installing the SOD, say June 15, and risk not watering for 6 days during vacation, OR, should I put off installing SOD after I get back July 6? Whaddda ya think?

In the scenario you explained, I would wait until you return. No sense worrying if Mother Nature will water your new lawn during your vacation. Hope you have a nice time!