Audrina Patridge in a Bikini -- The Hills Are Back!

Former "The Hills" actress Audrina Patridge took time off from her busy schedule of wearing a bikini in L.A. ... to show off her slammin' body in a white hot bikini at the ME Cabo Hotel in Mexico yesterday.

Audrina is down in Cabo San Lucas celebrating her 27th birthday with her BMX boyfriend Corey Bohan and some family members.