Danny,
I would prepare for the worst if you do Saddleback. Was in Rangeley over Memorial Day weekend and the afternoon/early evening black flies were unusually bad at times. Did not notice any mosquito activity then, but that could change too. Unlike black fliees, skeeters are easy to combat with DEET, as you probably know.
My recommendations are:
a. Getting an early start is always a good idea for the black flies, as they are not very active in cooler weather (typically less than 55 degrees).
b. Wearing a headnet will greatly reduce the black fly annoyance factor.
Good luck,
marty