Only since hanging out with a bunch of Californians have I begin to accept "guy" as applying to both genders. Before that, a guy was a guy, meaning male. Remember, "Guys and Dolls." Guys was not multi-gender then.
So I have come to find that Californians speak a different language, like people from Oz but with a different accent.
I read in the paper that a female student at one of the Los Angeles universities considered it offensive and sexual harassment to be called a "guy" by her professor, and sued. She was laughed out of court, but in Boston she may well have won.