Thanks for all the replies. Here are some answers:

No, I did not see any allen screws on the rotor. I have read other posts that mention these, but I can't find any.

I really don't want to replace the rotors, but I thought that would be the next logical step to get rid of the squeal.

I checked into the price of new rotors. NAPA wants $70 each and the MB dealer wants almost $150 each. I live in Hawaii which explains the ridiculous price. It costs $15 each to have them turned, so that's why I would rather do that.

Maybe I should try the anti-squeal spray stuff first...