Can an Investigator choose to "evade monster" prior to combat if he has 0 dice to roll for this skill check (thereby automatically receiving the monster's combat damage)?

Yes, and that me a tactically sound option, such as with a Nightgaunt .

Fluff-wise, I picture an investigator running away trying not to look at the monster.

I hear the sound of Bill Cosby's voice…of course, you would have to know his comedy records of the 1960s…but yeah, running away, yelling, "yahhhhhhhh!!!!"

Whenever Michael McGlen succeeds on a Horror check he really shouldn't have, I like to imagine he's too stupid to realize it's a monster. "Man, the fellas in this joint sure are ugly lookin'."

and that's what makes his Personal Story brilliant!