No, it is not here but on http://en.miui.com. And updates will be weekly in the future.
Starting from 18.07.2016 "MIUI 8 Global Beta ROM is to be updated weekly, instead of biweekly"
MIUI 8 Global Public Beta Supported Devices
Redmi 1S, Redmi 2, Redmi 2 Prime, Mi 3, Mi 4, Redmi Note 3...