While I'm sure that our water is considerably warmer than what you dive in MI, I also wouldn't dive in SoCal in less than 7mm.awall54308:I think I'll take everyones advice and bring my 7mm with me. However, being a Michigan diver, 60° sounds warm!!!
Aside from some of the unusually warm or cold stretches, the water is usually somewhere between 52º and 57º. Last year, I think I remember seeing temperatures in the 70º range as well as in 48º range.
7mm should have you feeling good.
Christian