Ever since Jennie B. told us about www.ourbestbites.com I've become addicted. They have so many yummy recipes. I originally got this recipe from that site, then made a few tweaks so it's a little bit healthier. This is similar to the dressing they have at Costa Vida.
1 pack (1oz) Hidden Valley Ranch Dressing Mix (ignore directions on the packet)
1/2 cup light mayo
1/2 cup plain yogurt
1/2 cup milk
2 cloves garlic roughly chopped
1/2 cup roughly chopped cilantro
1/4 cup green salsa
Place milk, mayo, yogurt, and ranch mix in a blender. I accidently grabbed a ranch dip pkt. instead of a ranch dressing pkt, but it worked just fine. Juice the lime in there, you should get about 2T juice. Toss in the garlic, cilantro and green salsa. Blend it until smooth. Make it several hours ahead of time to allow it to thicken.