Assuming the fog clears out, am I better off going to a dark sky site
or simply viewing from my suburban San Diego back yard? I guess the
real question for those of you with more experience is, how much will
I gain by making the trip east?

The moon rises at 10:30pm on July 4. Not too bad, might get in a hour and a
half of observing...

Of course, if its cloudy in San Diego, you will gain a lot. If it is not
cloudy, the air will be more transparent and less haze, something of an
advantage.

But if it clear in San Diego, the moon is too bright, not such a great target
but double stars are always fun and the various clusters in Scorpius and
Saggitarius (and all the others) provide some fun. And then there is the Ring
and the Dumbbell, M56 and M71.

Best thing to do:

See for yourself, thats the only way you can know.

jon