Miki Garcia isn't the kind of girl you meet every day. Oh, she's the usual melting-pot mixture (English, Irish, French and Spanish, in her case) and she likes the usual things (popcorn, Tom Jones, All in the Family). But how many women--or men--you know could sustain Miki's frenetic pace? Besides working at two jobs--as a Sacramento model and an insurance underwriter--25-year-old Miki is an amateur lobbyist for homeless animals, civic fund raiser, volunteer instructor for a class of Mexican-American teenaged girls who want to break into the modeling field, assistant director of an annual beauty pageant and owner of three hens, three cats, four pigeons, a rooster and a pair of rabbits. Miki is so busy, in fact, that after winning a dozen contest titles, she turned down the 13th and biggest, that of Miss California World--not because she's superstitious but because it would have conflicted with other commitments, foremost of which was her date to be a Playmate. Miki grew up as an Air Force brat, living in ten cities in four countries before settling in the Sacramento area in 1968. Her Spanish surname, in a locale of lingering anti-chicano bias, caused her some minor problems at first. "Now that I'm better known in town, I do what I can to combat prejudice," she says. "Before the Miss California-Bikini contest, of which I'm assistant director, I combed the countryside making speeches at intertribal council and civic meetings, signing up Indian, Mexican and black contestants. I was sick of all-white beauty contests." This month, Miki and pageant director Jane Pope, a local PR consultant, plan to internationalize their bikini competition with a contest in Hong Kong. Another new side line is the Mikini swimsuit, designed by Miki and crocheted as a fund-raising project by women from a predominantly black Baptist church. What makes Miki run? "I'm not really an activist," she says. "I just want to help people. But this pace is beginning to get to me. Like last night: One of my hens refused to sit, and I was up till all hours hatching eggs under an electric blanket, then feeding chicks with an eye dropper. I'm a wreck." We disagree.